LABORATORY REAGENTS FOR GENERAL USE

 

DILUTE ACIDS

3 molar. Use the amount of concentrated acid indicated and dilute to one liter.
Acetic acid, 3 N. Use 172 ml of 17.4 M acid (99-100%).
Hydrochloric acid, 3 N. Use 258 ml of 11.6 M acid (36% HCI).
Nitric acid, 3 N. Use l95 ml of 15.4 M acid (69% HNO3).
Phosphoric acid, 9 N. Use 205 ml of 14.6 M acid (85% H3PO4)
Sulfuric acid, 6 N. Use 168 ml of 17.8 M acid (95% H2SO4)

DILUTE BASES

Ammonium hydroxide, 3 M, 3 N. Dilute 200 ml of concentrated solution (14.8 M, 28% NH3) to 1 liter.
Barium hydroxide, 0.2 M, 0.4 N. Saturated solution, 63 g per liter of Ba(OH)2.8H2O. Use some excess, filter off BaCO3 and protect from CO2 of the air with soda lime or ascarite in a guard tube.
Calcium hydroxide, 0.02 M, 0.04 N>. Saturated solution, 1.5 g per liter of Ca(OH)2. Use some excess, filter off CaCO3 and protect from CO2 of the air.
Potassium hydroxide, 3 M, 3 N. Dissolve 176 g of the sticks (95%) in water and dilute to 1 liter.
Sodium hydroxide, 3 M, 3 N. Dissolve 126 g of the sticks (95%) in water and dilute to 1 liter.

GENERAL REAGENTS (See also Decinormal Solutions of Salts and other Reagents)

Aluminum chloride, 0.167 M, solve 22 g of AlC13 in 1 liter of water.
Aluminum nitrate, 0.167 M, 0.5 N. Dissolve 58 g of Al(NO3)3.7.5H20 in 1 liter of water.
Aluminum sulfate, 0.083 M, 0.5 N. Dissolve 56 g of Al2(SO4)3.18H2O in 1 liter of water.
Ammonium acetate, 3 M, 3 N. Dissolve 230 g of NH4C2H2O2 in water and dilute to 1 liter.
Ammonium carbonate, 1.5 M. Dissolve 144 g of the commercial salt (mixture of (NH4)2CO3.H,O and NH4CO2NH2) in 500 ml of 3 N NH4OH and dilute to 1 liter.
Ammonium chloride, 3 M, 3 N. Dissolve 160 g of NH4Cl in water. Dilute to 1 liter.
Ammonium molybdate:

1. 0,5 M, 1 N. Mix well 72 g of pure MoO5 (or 81 g of H2MoO4) with 200 ml of water, and add 60 ml of conc. ammonium hydroxide. When solution is complete, filter and pour filtrate, very slowly and with rapid stirring, into a mixture of 270 ml of conc. HNO3 and 400 ml of water. Allow to stand over night, filter and dilute to 1 liter.
2. The reagent is prepared as two solutions which are mixed as needed, thus always providing fresh reagent of proper strength and composition. Since ammonium molybdate is an expensive reagent, and since an acid solution of this reagent as usually prepared keeps for only a few days, the method proposed will avoid loss of reagent and provide more certain results for quantitative work.
Solution 1: Dissolve 100 g of ammonium molybdate (C.P. grade) in 400 ml of water and 80 ml of 15 M NH4OH. Filter if necessary, though this seldom has to be done
Solution 2: Mix 400 ml of 16 M nitric acid with 600 ml of water.

For use, mix the calculated amount of solution 1 with twice its volume of solution 2, adding solution 1 to solution 2 slowly with vigorous stirring. Thus, for amounts of phosphorus up to 20 mg, 10 ml of solution 1 to 20 ml of solution 2 is adequate. Increase amount as needed.
Ammonium nitrate, 1 M, 1 N. Dissolve 80 g of NH4NO3 in 1 liter of water.
Ammonium oxalate, 0.25 M, 0.5 N. Dissolve 35.5 g of (NH4)2C2O4.H2O in water. Dilute to 1 liter.
Ammonium sulfate, 0.25 M, 0,5 N. Dissolve 33 g of (NH4)2SO4 in 1 liter of water.
Ammonium sulfide, colorless:

1. 3 M. Treat 200 ml of conc. NH4OH with H2S until saturated, keeping the solution cold. Add 200 ml of conc. NH4OH and dilute of 1 liter.
2. 6 N. Saturate 6 N ammonium hydroxide (40 ml conc. ammonia solution +60 ml H2O) with washed H2S gas. The ammonium hydroxide bottle must be completely full and must be kept surrounded by ice while being saturated (about 48 hours for two liters). The reagent is best preserved in brown, completely filled, glas-stoppered bottles.

Ammonium sulfide, yellow:
Treat 150 ml of conc. NH4OH with H2S until saturated, keeping the solution cool. Add 250 ml of conc. NH4OH and 10 g of powdered sulfur. Shake the mixture until the sulfur is dissolved and dilute to 1 liter with water. In the solution the concentration of (NH4)2S2, (NH4) 2S and NH4OH are 0.625, 0.4 and 1.5 normal respectively. On standing, the concentration of (NH4)2S2 increases and that of (NH4)2S and NH4OH decreases.
Antimony pentachloride, 0.1 M, 0.5 N. Dissolve 30 g of SbCl5 in 1 liter of water
Antimony trichloride, 0.167 M, 0.5 N. Dissolve 38 g of SbC13 in 1 liter of water.
Aqua regia. Mix 1 part concentrated HNO3 with 3 parts of concentrated HCl. This formula should include one volume of water if the aqua regia is to be stored for any length of time. Without water, objectionable quantities of chlorine and other gases are evolved.
Barium chloride, 0.25 M, 0.5 N. Dissolve 61 g of BaCl2.2H2O in water. Dilute to 1 liter.
Barium hydroxide, 0,1 M, about 0.2 N. Dissolve 32 g of Ba(OH)2.8H2O in 1 liter of water.
Barium nitrate, 0.25 M, 0.5 N. Dissolve 65 g of Ba(NO3)2 in 1 liter of water.
Bismuth chloride, 0.167 M, 0.5 N. Dissolve 53 g of BiCl2 in 1 liter of dilute HCl, Use 1 part HCI to 5 parts water.
Bismuth nitrate, 0.083 M, 0.25 N. Dissolve 40 g of Bi(NO3)3.5H2O in 1 liter of dilute HNO3, Use 1 part of HNO3 to 5 parts of water.
Cadmium chloride, 0,25 M, 0.5 N. Dissolve 46 g of CdC12 in 1 liter of water.
Cadmium nitrate, 0.25 M, 0.5 N. Dissolve 77 g of Cd(NO3) 2.4H2O in 1 liter of water.
Cadmium sulfate, 0.25 M, 0.5 N. Dissolve 70 g of CdSO4. 4H2O in 1 liter of water.
Calcium chloride, 0.25 M, 0.5 N. Dissolve 55 g of CaCl2.6H20 in water. Dilute to 1 liter.
Calcium nitrate, 0.25 M, 0.5 N. Dissolve 41 g of Ca(NO3)2 in 1 liter of water.
Chloroplatinic acid:

1. 0.0512 M, 0.102 N. Dissolve 26.53 g of H2PtCl4.6H2O in water. Dilute to 100 ml. Contains 0.100 g Pt per ml
2. Make a 10% solution by dissolving 1 g of H2PtCl6.6H2O in 9 ml of water. Shake thoroughly to insure complete mixing. Keep in a dropping bottle.

Chromic chloride, 0.167 M, 0.5 N. Dissolve 26 g of CrCl3 in 1 liter of water.
Chromic nitrate, 0.167 M, 0.5 N. Dissolve 40 g of Cr(NO3) 3 in 1 liter of water.
Chromic sulfate, 0.083 M, 0.5 N. Dissolve 60 g of Cr2(SO4)3.18H2O in 1 liter of water.
Cobaltous nitrate, 0.25 M, 0.5 N. Dissolve 73 g of Co(NO3)2.6H2O in 1 liter of water.
Cobaltous sulfate, 0.25 M, 0.5 N. Dissolve 70 g of CoSO4.7H2O in 1 liter of water.
Cupric chloride, 0.25 M, 0.5 N. Dissolve 43 g of CuCl2.2H2O in 1 liter of water.
Cupric nitrate, 0.25 M, 0.5 N. Dissolve 74 g of Cu(NO3)2. 6H2O in 1 liter of water.
Cupric sulfate, 0.5 M, 1 N. Dissolve 124. g of CuSO4.5H2O in water to which 5 ml of H2SO4 has been added. Dilute to 1 liter.
Ferric chloride, 0.5 M, 1.5 N. Dissolve 135.2 g of FeCl3.6H2O in water containing 20 ml of conc. HCl. Dilute to1 liter.
Ferric nitrate, 0.167 M, 0.5 N. Dissolve 67 g of Fe(NO3)3 9H2O in 1 liter of water.
Ferric sulfate, 0.25 M, 0.5 N. Dissolve 140.5 g of Fe3(SO4)3.9H2O in water containing 100 ml of conc. H2SO4. Dilute to 1 liter.
Ferrous ammonium sulfate, 0.5 M, 1 N. Dissolve 196 g of Fe(NH4SO4)2.6H2O in water containing 10 ml of conc. H2SO4. Dilute to 1 liter. Prepare fresh solutions for best results
Ferrous sulfate, 0.5 M, 1 N. Dissolve 139 g of FeSO4.7H2O in water containing 10 ml of conc. H2SO4. Dilute to 1 liter. Solution does not keep well.
Lead acetate, 0.5 M, 1 N. Dissolve 190 g of Pb(C2H3O2)2. 3H2O in water. Dilute to 1 liter.
Lead nitrate, 0.25 M, 0.5 N. Dissolve 83 g of Pb(NO2)2 in water. Dilute to one liter.
Lime water. See Calcium hydroxide.
Magnesium chloride, 0.25 M, 0.5 N. Dissolve 51 g of MgCI2.6H2O in 1 liter of water.
Magnesium chloride reagent. Dissolve 50 g of MgC2.6H20 and 100 g of NH4Cl in 500 ml of water. Add 10 ml of conc. NH4OH, allow to stand over night and filter if a precipitate has formed. Make acid to methyl red with if a dilute HCl. Dilute to 1 liter. Solution contains 0.25 M MgCl2 and 2 M NH4Cl. Solution may also be diluted with 133 ml of conc. NH4OH and water to make 1 liter. Such a solution will contain 2 M NH4OH.
Magnesium nitrate, 0.25 M, 0.5 N. Dissolve 64 g of Mg(NO2)2.6H2O in 1 liter of water.
Magnesium sulfate, 0.25 M, 0.5 N. Dissolve 62 g of MgSO4.7H2O in 1 liter of water.
Manganous chloride, 0.25 M, 0.5 N. Dissolve 50 g of MnCl2.4H2O in 1 liter of water.
Manganous nitrate, 0.25 M, 0.5 N. Dissolve 72 g of Mn(NO3)2.6H2O in 1 liter of water.
Manganous sulfate, 0.25 M, 0.5 N. Dissolve 69 g of MnSO4.7H2O in 1 liter of water.
Mercuric chloride, 0.25 M, 0.5 N. Dissolve 68 g of HgCl2 in water. Dilute to 1 liter.
Mercuric nitrate, 0.25 M, 0.5 N. Dissolve 81 g of Hg(NO3)2 in 1 liter of water.
Mercuric sulfate, 0.25 M, 0.5 N. Dissolve 74 g of HgSO4 in 1 liter of water.
Mercurous nitrate. Use 1 part HgNO3, 20 parts water and 1 part HNO3.
Nickel chloride, 0.25 M, 0.5 N. Dissolve 59 g of NiCI26H2O in 1 liter of water.
Nickel nitrate, 0.25 M, 0.5 N. Dissolve 73 g of Ni(NO3)2.-6H2O in 1 liter of water.
Nickel sulfate, 0.25 M, 0.5 N. Dissolve 66 g of NiSO4.6H2O in 1 liter of water.
Potassium bromide, 0.5 M, 0.5 N. Dissolve 60 g of KBr in 1 liter of water.
Potassium carbonate, 1.5 M, 3 N. Dissolve 207 g of K2CO3 in 1 liter of water.
Potassium chloride, 0.5 M, 0.5 N. Dissolve 37 g of KCI in 1 liter of water.
Potassium chromate, 0.25 M, 0.5 N. Dissolve 49 g of K2CrO4 in 1 liter of water.
Potassium cyanide, 0.5 M, 0.5 N. Dissolve 33 g of KCN in 1 liter of water.
Potassium dichromate, 0.125 M. Dissolve 37 g of K2Cr2O7 in 1 liter of water.
Potassium ferricyanide, 0.167 M, 0.5 N. Dissolve 55 g of K3Fe(CN)6 in 1 liter of water.
Potassium ferrocyanide, 0.5 M, 2 N. Dissolve 211 g of K4Fe(CN)6.3H2O in water. Dilute to 1 liter.
Potassium iodide, 0.5 M, 0.5 N. Dissolve 83 g of KI in 1 liter of water.
Potassium nitrate, 0.5 M, 0.5 N. Dissolve 51 g of KNO3 in 1 liter of water.
Potassium sulfate, 0.25 M, 0.5 N. Dissolve 44 g of K2SO4 in 1 liter of water.
Silver nitrate, 0.5 M, 0.5 N. Dissolve 85 g of AgNO3 in water. Dilute to 1 liter.
Sodium acetate, 3 M, 3 N. Dissolve 408 g of NaC2H3O2.3H2O in water. Dilute to 1 liter.
Sodium carbonate, 1.5 M, 3 N. Dissolve 159 g of Na2CO3, or 430 g of Na2CO3.10H2O in water. Dilute to 1 liter.
Sodium chloride, 0.5 M, 0.5 N. Dissolve 29 g of NaCl in 1 liter of water.
Sodium cobaltinitrite, 0.08 M (reagent for potassium). Dissolve 25 g of NaNO2 in 75 ml of water, add 2 ml of glacial acetic acid and then 2.5g of Co(NO3)2.6H2O. Allow to stand for several days, filter and dilute to 100 ml. Reagent is somewhat unstable.
Sodium hydrogen phosphate, 0.167 M, 0.5 N. Dissolve 60 g of Na2HPO4.12H2O in 1liter of water.
Sodium nitrate, 0.5 M, 0.5 N. Dissolve 43 g of NaNO3 in 1 liter of water.
Sodium sulfate, 0.25 M, 0.5 N. Dissolve 36 g o? Na2SO4 in 1 liter of water.
Sodium sulfide, 0.5 M, 1 N. Dissolve 120 g of Na2S.9H2O in water and dilute to 1 liter. Or, saturate 500 ml of 1 M NaOH (21 g of 95% NaOH sticks) with H2S, keeping the solution cool, and dilute with 500 ml of 1 M NaOH.
Stannic chloride, 0.125 M, 0.5 N. Dissolve 33 g of SnCl4 in 1 liter of water.
Stannous chloride, 0.5 M, 1 N. Dissolve 113 g of SnCl2.2H2O in 170 ml of cone. HCl, using heat if necessary. Dilute with water to 1 liter. Add a few pieces of tin foil. Prepare solution fresh at frequent intervals.
Stannous chloride (for Bettendorf test). Dissolve 113 g of SnCl2.2H2O in 75 ml of conc. HCl. Add a few pieces of tin foil.
Strontium chloride, 0.25 M, 0.5 N. Dissolve 67 g of SrCl2.6H2O in 1 liter of water.
Zinc nitrate, 0.25 M, 0.5 N. Dissolve 74 g of Zn(NO3)2.6H2O in 1 liter of water.
Zinc sulfate, 0.25 M, 0.5 N. Dissolve 72 g of ZnSO4.7H2O in 1 liter of water.

SPECIAL SOLUTIONS AND REAGENTS

a-Naphthol (Molisch’s reagent for wool). Dissolve 15 g of a-naphthol in 100 ml of alcohol or chloroform.
a-Nitroso-b-naphthol. Make a saturated solution in 50 % acetic acid (1 part of glacial acetic acid with 1 part of water). Does not keep well.
Aluminon (qualitative test for aluminum). Aluminon is a trade name for the ammonium salt of aurin tricarboxylic acid. Dissolve 1 g of the salt in 1 liter of distilled water. Shake the solution well to insure thorough mixing.
Bang’s reagent (for glucose estimation). Dissolve 100 g of K2CO3, 66 g of KCl and 160 of KHCO3 in the order given in about 700 ml of water at 30° C. Add 4.4 g of CuSO4 and dilute to 1 liter after the CO2 is evolved. This solution should be shaken only in such a manner as not to allow entry of air. After 24 hours 300 ml are diluted to 1 liter with saturated KCl solution, shaken gently and used after 24 hours; 50 ml equivalent to 10 mg glucose.
Barfoed’s reagent (test for glucose). See Cupric acetate.
Baudisch’s reagent. See Cupferron.
Benedict’s solution (qualitative reagent for glucose). With the aid of heat, dissolve 173 g of sodium citrate and 100 g of Na2CO3 in 800 ml of water. Filter, if necessary, and dilute to 850 ml. Dissolve 17.3 gof CuSO4.5H2O in 100 ml of water. Pour the latter solution, with constant stirring, into the carbonate-citrate solution, and make up to 1 liter.
Benzidine hydrochloride solution (for sulfate determination). Make a paste of 8 g of benzidine hydrochloride (C12H8(NH2)2.2HCl) and 20 ml of water, add 20 ml of HCI (sp. gr. 1.12) and dilute to 1 liter with water. Each ml of this solution is equivalent to 0.00357 g of H2SO4.
Bertrand’s reagent (glucose estimation). Consists of the following solutions:

(a) Dissolve 200 g of Rochelle salts and 150 g of NaOH in sufficient water to make 1 liter of solution.
(b) Dissolve 40 g of CuSO4 in enough water to make 1 liter of solution.
(c) Dissolve 50 g of Fe2(SO4)3 and 200 g of H2SO4 (sp. gr. 1.84) in sufficient water to make 1 liter of solution.
(d) Dissolve 5 g of KMnO4 in sufficient water to make 1 liter of solution.

Blal’s reagent (for pentose). Dissolve 1 g of orcinol (CH3.C6H3(OH)2) in 500 ml of 30% HCl to which 30 drops of a 10% solution of FeCl3 has been added.
Boutron-Boudet soap solution:

(a) Dissolve 100 g of pure castile soap in about 2500 ml of 56% ethyl alcohol.
(b) Dissolve 0.59 g of Ba(NO3)2 in 1 liter of water.
Adjust the castile soap solution so that 2.4 ml of it will give a permanent lather with 40 ml of solution (b). When adjusted 2.4 ml of soap solution is equivalent to 220 parts per million of hardness (as CaCO3) for a 40 ml sample.
See also Soap solution.

Brucke’s reagent (protein precipitation). See Potassium iodide-mercuric iodide.
Clarke’s soap solution (or A.P.H.A. standard method). Estimation of hardness in water:

(a) Dissolve 100 g of pure powdered castile soap in 1 liter of 80% ethyl alcohol and allow to stand overnight.
(b) Prepare a standard solution of CaCl2 by dissolving 0.5 of CaCO3 in HCl (sp. gr. 1.19), neutralize with NH4OH and make slightly alkaline to litmus, and dilute to 500 ml. One ml is equivalent to 1 mg of CaCO3.
Titrate (a) against (b)and dilute (a) with 50% ethyl alcohol until 1 ml of the resulting solution is equivalent to 1 ml of (b) after making allowance for the lather factor (the amount of standard soap solution required to produce a permanent lather in 50 ml of destilled water). One ml of the adjusted solution after subtracting the lather factor is equivalent to 1 mg of CaCO3.
See also Soap solution.

Cobalticyanide paper (Rinnmann ‘s test for Zn). Dissolve 4 g of K2Co(CN)5 and 1 g of KClO3 in 100 ml of water. Soak filter paper in solution and dry at 100° C. Apply drop of zinc solution and burn in an evaporating dish. A green disk is obtained if zinc is present.
Cochineal. Extract 1 g of cochineal for four days with 20 ml of alcohol and 60 ml of distilled water. Filter.
Congo red. Dissolve 0.5 g of congo red in 90 ml of destilled water and 10 ml of alcohol.
Cupferron (Baudisch ‘s reagent for iron analysis). Dissolve 6 g of the ammonium salt of nitroso-phenyl-hydroxyl-amine (cupferron) in 100 ml of H2O. Reagent good for one week only and must be kept in the dark.
Cupric acetate (Barfoed’s reagent for reducing monosaccharides). Dissolve 66 g of cupric acetate and 10 ml of glacial acetic acid in water and dilute to 1 liter.
Cupric oxide, ammoniacal; Schweitzer’s reagent (dissolves cotton, linen and silk, but not wool):

1. Dissolve 5 g of cupric sulfate in 100 ml of boiling water, and add sodium hydroxide until precipitation is complete. Wash the precipitate well, and dissolve it in a minimum quantity of ammonium hydroxide.
2. Bubble a slow stream of air through 300 ml of strong ammonium hydroxide containing 50 g of fine copper turnings. Continue for one hour.

Cupric sulfate in glycerin-potassium hydroxide (reagent for silk). Dissolve 10 g of cupric sulfate, CuSO4.5H2O, in 100 ml of water and add 5 g of glycerin. Add KOH solution slowly until a deep blue solution is obtained.
Cupron (benzoin oxime). Dissolve 5 g in 100 ml of 95 % alcohol.
Cuprous chloride, acidic (reagent for CO in gas analysis):

1. Cover the bottom of a two-liter flask with a layer of cupric oxide about one-half inch deep, suspend a bunch of copper wire so as to reach from the bottom to the top of the solution, and fill the flask with hydrochloric acid (sp. gr. 1.10). Shake occasionally. When the solution becomes nearly colorless, transfer to reagent bottles, which should also contain copper wire. The stock bottle may be refilled with dilute hydrochloric acid until either the cupric oxide or the copper wire is used up.
Copper sulfate may be substituted for copper oxide in the above procedure.
2. Dissolve 340 g of CuC12.2H2O in 600 ml of conc. HCl and reduce the cupric chloride by adding 190 ml of a saturated solution of stannous chloride or until the solution is colorless. The stannous chloride is prepared by treating 300 g of metallic tin in a 500 ml flask with conc. HCl until no more tin goes into solution.
3. (Winkler method). Add a mixture of 86 g of CuO and 17 g of finely divided metallic Cu, made by the reduction of CuO with hydrogen, to a solution of HCl, made by diluting 650 ml of conc. HCl with 325 ml of water. After the mixture has been added slowly and with frequent stirring, a spiral of copper wire is suspended in the bottle, reaching all the way to the bottom. Shake occasionally, and when the solution becomes colorless, it is ready for use.

Cuprous chloride, ammoniacal (reagent for CO in gas analysis):

1. The acid solution of cuprous chloride as prepared above is neutralized with ammonium hydroxide until an ammonia odor persists. An excess of metallic copper must be kept in the solution.
2. Pour 800 ml of acidic cuprous chloride, prepared by the Winkler method, into about 4 liters of water. Transfer the precipitate to a 250 ml graduate. After several hours, siphon off the liquid above the 50 ml mark and refill with 7.5% NH4OH solution which may be prepared by diluting 50 ml of conc. NH4OH with 150 ml of water. The solution is well shaken and allowed to stand for several hours. It should have a faint odor of ammonia.

Dichlorfluorescin indicator. Dissolve 1 g in 1 liter of 70% alcohol or 1 g of the sodium salt in 1 liter of water.
Dimethylglyoxime (diacetyl dioxime), 0.01 N. Dissolve 0.6 g of dimethylglyoxime, (CH3CNOH)2, in 500 ml of 95 % ethyl alcohol. This is an especially sensitive test for nickel, a very definite crimson color being produced.
Diphenylamine (reagent for rayon). Dissolve 0.2 g in 100 ml of concentrated sulfuric acid.
Diphenylamine sulfonate (for titration of iron with K2Cr2O7). Dissolve 0.32 g of the barium salt of diphenylamine sulfonic acid in 100 ml of water, add 0.5 g of sodium sulfate and filter off the precipitate of BaSO4.
Diphenylcarbazide. Dissolve 0.2 g of diphenylcarbazide in 10 ml of glacial acetic acid and dilute to 100 ml with 95% ethy1 alcohol.
Esbach’s reagent (estimation of protein). To a water solution of 10 g of picric acid and 20 g of citric acid, add sufficient water to make one liter of solution.
Eschka’s compound. Two parts of calcined (“light”) magnesia are thoroughly mixed with one part of anhydrous sodium carbonate.
Fehling’s solution. (reagent for reducing sugars):

(a) Copper sulfate solution. Dissolve 34.66 g of CuSO4 5H2O in water and dilute to 500 ml.
(b) Alkaline tartrate solution. Dissolve 173 g of potassium sodium tartrate (Rochelle salts, KNaC4H4O6.4 H2O) and 50 g of NaOH in water and dilute when cold to 500 ml.
For use, mix equal volumes of the two solutions at the time of using.

Ferric-alum indicator. Dissolve 140 g of ferric-ammonium sulfate crystals in 400 ml of hot water. When cool, filter, and make up to a volume of 500 ml with dilute (6 N) nitric acid.
Folin’s mixture. (for uric acid). To 650 ml of water add 500 g of (NH4)2SO4, 5 g of uranium acetate and 6 g of glacial acetic acid. Dilute to 1 liter.
Formaldehyde-sulfuric acid (Marquis’ reagent for alkaloids). Add 10 ml of formaldehyde solution to 50 ml of sulfuric acid.
Froehde’s reagent. See Sulfomolybdic actid.
Fuchsin (reagent for linen). Dissolve 1 g of fuchsin in 100 ml of alcohol.
Fuchsin-sulfurous acid (Schiff’s reagent for aldehydes). Dissolve 0.5 g of fuchsin and 9 g of sodium bisulfite in 500 ml of water, and add 10 ml of HCI. Keep in well-stoppered bottles and protect from light.
Gunzberg’s reagent (detection of HCl in gastric juice). Prepare as needed a solution containing 4 g of phloroglucinol and 2 g of vanillin in 100 ml of absolute ethyl alcohol.
Hager’s reagent. See Picric acid.
Hanus solution (for iodine number). Dissolve 13.2 g of resublimed iodine in one liter of glacial acetic acid which will pass the dichromate test for reducible matter. Add sufficient bromine to double the halogen content, determined by titration (3 ml is about the proper amount). The iodine may be dissolved by the aid of heat, but the solution should be cold when the bromine is added.
Iodine, tincture of. To 50 ml of water add 70 g of I2 and 50 g of KI. Dilute to 1 liter with alcohol.
Iodo-potasium iodide (Wagner’s reagent for alkaloids). Dissolve 2 g of iodine and 6 g of KI in 100 ml of water.
Litmus (indicator). Extract litmus powder three times with boiling alcohol, each treatment consuming an hour. Reject the alcoholic extract. Treat residue with an equal weight of cold water and. filter; then exhaust with five times its weight of boiling water, cool and filter. Combine the aqueous extracts.
Magnesia mixture (reagent for phosphates and arsenates). Dissolve 55 g of magnesium chloride and 105 g of ammonium chloride in water, barely acidify with hydrochloric acid, and dilute to 1 liter. The ammonium hydroxide may be omitted until just previous to use. The reagent, if completely mixed and stored for any period of time, becomes turbid.
Magnesium reagent. See S and O reagent.
Magnesium uranyl acetate. Dissolve 100 g of UO2(C2H3O2)2.2H2O in 60 ml of glacial acetic acid and dilute to 500 ml. Dissolve 330 g of Mg(C2H3O2)2.4H2O in 60 ml of glacial acetic acid and dilute to 200 ml. Heat solutions to the boiling point until clear, pour the magnesium solution into time uranyl solution, cool and dilute to l liter. Let stand over night and filter if necessary.
Marme’s reagent. See Potassium-cadmium iodide.
Marqui’s reagent. See Formaldehyde-sulfuric acid.
Mayer’s reagent. (white precipitate with most alkaloids in slightly acid solutions). Dissolve 1.358 g of HgCl2 in 60 ml of water and pour into a solution of 5 g of KI in 10 ml of H2O Add sufficient water to make 100 ml.
Methyl orange indicator. Dissolve 1 g of methyl orange in 1 liter of water. Filter, if necessary.
Methyl orange, modified. Dissolve 2 g of methyl orange and 2.8 g of xylene cyanole FF in 1 liter of 50% alcohol.
Methyl red indicator. Dissolve 1 g of methyl red in 600 ml of alcohol and dilute with 400 ml of water.
Methyl red, modified. Dissolve 0.50 g of methyl red and 1.25 g of xylene cyanole FF in 1 liter of 90% alcohol. Or, dissolve 1.25 g of methyl red and 0.825 g of methylene blue in 1 liter of 90% alcohol.
Millon’s reagent (for albumins and phenols). Dissolve 1 part of mercury in 1 part of cold fuming nitric acid. Dilute with twice the volume of water and decant the clear solution after several hours.
Mixed indicator. Prepared by adding about 1.4 g of xyleno cyanole FF to 1 g of methyl orange. The dye Is seldom pure enough for these proportion to be satisfactory. Each new lot of dye should be tested by adding additional amounts of the dye until test portion gives the proper color change. The acid color of this indicator Is like that of permanganate; the neutral color is gray; and the alkaline color Is green. Described by Hickman and Linstead, J. Chem. Soc. (Lon.), 121, 2502 (1922).
Molisch’s reagent. See a-Naphthol.
Nessler’s reagent (for ammoniak). Dissolve 50 g of KI in the smallest possible quantity of cold water (50 ml). Add a saturated solution of mercuric chloride (about 22 g in 350 ml of water will be needed) until an excess is indicated by the formation of a precipitate. Then add 200 ml of 5 N NaOH and dilute to 1 liter. Let settle, and draw off the clear liquid.
Nickel oxide, ammoniacal (reagent for silk). Dissolve 5 g of nickel sulfate in 100 ml of water, and add sodium hydroxide solution until nickel hydroxide is completely precipitated Wash the precipitate well and dissolve in 25 ml of concentrated ammonium hydroxide and 25 ml of water.
Nitron (detection of nitrate radical). Dissolve 10 g of nitron (C20H16N4, 4,5-dihydro-l,4-diphenyl-3,5-phenylimino-1,2,4-triazole) in 5 ml of glacial acetic acid and 95 ml of water. The solution may be filtered with slight suction through an alundum crucible and kept in a dark bottle.
Nylander’s solution (carbohydrates). Dissolve 20 g of bismuth subnitrate and 40 g of Rochelle salts in 1 liter of 8% NaOH solution. Cool and filter.
Obermayer’s reagent (for indoxyl in urine). Dissolve 4 g of FeCl3 in one liter of HCI (sp. gr. 1.19).
o-Tolidine solution (residual chlorine in water analysis). Prepare 1 liter of dilute HCl (100 ml of HCl (sp. gr. 1.19) in sufficient water to make 1 liter). Dissolve 1 g of o-tolidine in 100 ml of the dilute HCl and dilute to 1 liter with dilute HCl solution.
Oxine. Dissolve 14 g of HC9H6ON in 30 ml of glacial acetic acid. Warm slightly, if necessary. Dilute to 1 liter.
Oxygen absorbent. Dissolve 300 g of ammonium chloride in one liter of water and add one liter of concentrated ammonium hydroxide solution. Shake the solution thoroughly. For use as an oxygen absorbent, a bottle half full of copper turnings is filled nearly full with the NH4CI-NH4OH solution and the gas passed through.
Pasteur’s salt solution. To one liter of distilled water add 2.5 g of potassium phosphate, 0.25 g of calcium phosphates, 0.25 g of magnesium sulfate and 12.00 g of ammonium tartrate.
Pavy’s solution (glucose reagent). To 120 ml of Fehling’s solution, add 300ml of NH4OH (sp. gr. 0.88) and dilute to 1 liter with water.
Phenanthroline ferrous ion indicator. Dissolve 1.485 g of phenanthroline monohydrate in 100 ml of 0.025 M ferrous sulfate solution.
Phenolphthalein. Dissolve 1 g of phenolphthalein in 50 ml of alcohol and add 50 ml of water.
Phenolsulfonic acid (determination of nitrogen as nitrate). Dissolve 25gof phenol in 150 ml of conc. H2SO4, add 75 ml of fuming H2SO4 (15% SO3), stir well and heat for two hours at l00 °C
Phloroglucinol solution (pentosans). Make a 3% phloroglucinol solution in alcohol. Keep in a dark bottle.
Phosphomolybdic acid (Sonnenschein ‘s reagent for alkaloids):

1. Prepare ammonium phosphomolybdate and after washing with water, boil with nitric acid and expel NH3; evaporate to dryness and dissolve in 2 N nitric acid.
2. Dissolve ammonium molybdate in HNO3, and treat with phosphoric acid. Filter, wash the precipitate, and boil with aqua regia until the ammonium salt is decomposed. Evaporate to dryness. The residue dissolved in 10% HNO3 constitutes Sonnenschein’s reagent.

Phosphoric acid – sulfuric acid mixture. Dilute 150 ml of conc. H2SO4 and 100 ml of conc. H3PO4 (85%) with water to a volume of 1 liter.
Phosphotungstic acid (Scheibler ‘s reagent for alkaloids):

1. Dissolve 20 g of sodium tungstate and 15 g of sodium phosphate in 100 ml of water containing a little nitric acid.
2. The reagent is a 10% solution of phosphotungstic acid in water. The phosphotungstic acid is prepared by evaporating a mixture of 10 g of sodium tungstate dissolved in 5 g of phosphoric acid (sp. gr. 1.13) and enough boiling water to effect solution. Crystals of phosphotungstic acid separate.

Picric acid (Hager’s reagent for alkaloids, wool and silk). Dissolve 1 g of picric acid in 100 ml of water.
p-Nitrobenzene-azo-resorcinol (reagent for magnesium). Dissolve 1 g of the dye in 10 ml of N NaOH and dilute to 1 liter.
Potassium antimonate (reagent for sodium). Boil 22 g of potassium antimonate with 1 liter of water until nearly all of the salt has dissolved, cool quickly, and add 35 ml of 10% potassium hydroxide. Filter after standing over night.
Potassium hydroxide (for CO2 absorption). Dissolve 360 g of KOH in water and dilute to 1 liter.
Potassium iodide-mercuric iodide (Brucke’s reagent for proteins). Dissolve 50 g of KI in 500 ml of water, and saturate with mercuric iodide (about 120 g). Dilute to I liter.
Potassium pyrogallate (for oxygen absorption). For mixtures of gases containing less than 28% oxygen, add 100 ml of KOH solution (50 g of KOH to 100 ml of water) to 5 g of pyrogallol. For mixtures containing more than 28% oxygen the KOH solution should contain 120 g of KOH to 100 ml of water.
Potassium-cadmium iodide (Marme ’s reagent for alkaloids). Add 2 g of CdI2 to a boiling solution of 4g of KI in 12 ml of water, and then mix with 12 ml of saturated KI solution.
Pyrogallol, alkaline:

(a) Dissolve 75 g of pyrogallic acid in 75 ml of water.
(b) Dissolve 500 g of KOH in 250 ml of water. When cool, adjust until sp. gr. is 1.55.
For use, add 270 ml of solution (b) to 30 ml of solution (a).

Rosolic acid (indicator). Dissolve 1 g of rosolic acid in 10 ml of alcohol and add l00 ml of water.
S and O reagent (Suitsu and Okuma ‘s test for Mg). Dissolve 0.5 g of the dye (o, p-dihydroxy-monoazo-p-nitrobenzene) in 100 ml of 0.25 NaOH.
Scheibler’s reagent. See Phosphotungstic acid.
Schiff’s reagent. See Fuchsin-sulfurous acid.
Schweitzer’s reagent. See Cupric oxide, ammoniacal
Soap solution (reagent for hardness in water). issolve 100 g of dry castile soap in 1 liter of 80% alcohol (5 parts alcohol to 1 part water). Allow to stand several days and dilute with 70% to 80% alcohol until 6.4 ml produces a permanent lather with 20 ml of standard calcium solution. The latter solution is made by dissolving 0.2 g of CaCO3 in a small amount of dilute HCl, evaporating to dryness and making up to 1 liter.
Sodium bismuthate (oxidation of manganese). Heat 20 parts of NaOH nearly to redness in an iron or nickel crucible and add slowly 10 parts of basic bismuth nitrate which has been previously dried. Add two parts of sodium peroxide, and pour the brownish-yellow fused mass on an iron plate to cool. When cold, break up in a mortar, extract with water, and collect on an asbestos filter.
Sodium hydroxide (for CO2 absorption). Dissolve 330 g of NaOH in water and dilute to 1 liter.
Sodium nitroprusside (reagent for hydrogen sulfide and wool). Use a freshly prepared solution of 1 g of sodium nitroprusside in 10 ml of water.
Sodium oxalate, according to Sörensen (primary standard). Dissolve 30 g of the commercial salt in 1 liter of water, make slightly alkaline with sodium hydroxide, and let stand until perfectly clear. Filter and evaporate the filtrate to 100 ml. Cool and filter. Pulverize the residue and wash it several times with small volumes of water. The procedure is repeated until the mother liquor is free from sulfate and is neutral to phenolphthalein.
Sodium plumbite (reagent for wool). Dissolve 5 g of sodium hydroxide in 100 ml of water. Add 5 g of litharge and boil until dissolved.
Sodium polysulfide. Dissolve 480 g of Na2S.9H20 in 500 ml of water, add 40 g of NaOH and 18 g of sulfur. Stir thoroughly and dilute to 1 liter with water.
Sonnenschein’s reagent. See Phosphomolybdic acid.
Starch solution:

1. Make a paste with 2 g of soluble starch and 0.01 g of HgI2 with a small amount of water. Add the mixture slowly to 1 liter of boiling water and boil for a few minutes. Keep in a glass stoppered bottle. If other than soluble starch is used, the solution will not clear on boiling; it should be allowed to stand and the clear liquid decanted.
2. A solution of starch which keeps indefinitely is made as follows: Mix 500 ml of saturated NaCI solution (filtered), 80 ml of glacial acetic acid, 20 ml of water and 3 g of starch. Bring slowly to a boil and boil for two minutes.
3. Make a paste with 1 g of soluble starch and 5 mg of HgI2, using as little cold water as possible. Then pour about 200 ml of boiling water on the paste and stir immediately. This will give a clear solution if the paste is prepared correctly and the water actually boiling. Cool and add 4g of KI. Starch solution decomposes on standing due to bacterial action, but this solution will keep a long time if stored under a layer of toluene.

Stoke’s reagent. Dissolve 30 g of FeSO4 and 20 g of tartaric acid in water and dilute to 1 liter. Just before using, add concentrated NH4OH until the precipitate first formed is redissolved
Sulfanilic acid (reagent for nitrites). Dissolve 0.5 g of sulfanilic acid in a mixture of 15 ml of glacial acetic acid and 135 ml of recently boiled water.
Sulfomolybdic acid (Froehde ‘s reagent for alkaloids and glucosides). Dissolve 10 g of molybdic acid or sodium molybdate in 100 ml of conc. H2SO4
Tannic acid (reagent for albumen, alkaloids and gelatin). Dissolve 10 g of tannic acid in 10 ml of alcohol and dilute with water to 100 ml.
Titration mixture. See Zimmermann-Reinhardt reagent.
Trinitrophenol solution. See Picric acid.
Turmeric paper. Impregnate white, unsized paper with the tincture, and dry.
Turmeric tincture (reagent for borates). Digest ground turmeric root with several quantities of water which are discarded. Dry the residue and digest it several days with six times its weight of alcohol. Filter.
Uffelmann’s reagent (turns yellow in presence of a lactic acid). To a 2% solution of pure phenol in water, add a water solution of FeCl3 until the phenol solution hecornes violet in color.
Wagner’s reagent. See Iodo-potassium iodide.
Wagner’s solution (used in phosphate rock analysis to prevent precipitation of iron and aluminum). Dissolve 25 g of citric acid and 1 g of salicylic acid in water and dilute to 1 liter. Use 50 ml of the reagent.
Wij’s iodine monochloride solution (for iodine number). Dissolve 13 g of resublimed iodine in 1 liter of glacial acetic acid which will pass the dichromate test for reducible matter. Set aside 25 ml of this solution. Pass into the remainder of the solution dry chlorine gas (dried and washed by passing through H2SO4 (sp. Gr. 1.84)) until the characteristic color of free iodine has been discharged. Now add the iodine solution which was reserved, until all free chlorine has been destroyed. A slight excess of iodine does little or no harm, but an excess of chlorine must be avoided. Preserve in well stoppered, amber colored bottles. Avoid use of solutions which have been prepared for more than 30 days.
Wij’s special solution (for iodine number-Analyst 58, 523-7, 1933). To 200 ml of glacial acetic acid that will pass the dichromate test for reducible matter, add 12 g of dichloroamine T (paratoluene-sulfonedichloroamide), and 16.6 g of dry KI (in small quantities with continual shaking until all the KI has dissolved). Make up to 1 liter with the same quality of acetic acid used above and preserve in a dark colored bottle.
Zimmermann-Reinhardt reagent (determination of iron). Dissolve 70 g of MnSO4.4H2O in 500 ml of water, add 125 ml of oonc.H2SO4 and 125 ml of 85% H3PO4, and dilute to 1 liter.
Zinc chloride solution, basic (reagent for silk). Dissolve 1000 g of zinc chloride in 850 ml of water, and add 40 g of zinc oxide. Heat until solution is complete.
Zinc uranyl acetate (reagent for sodium). Dissolve 10 of UO2(C2H3O2)2.2H2O in 6 g of 30 % acetic acid with heat, if necessary, and dilute to 50 ml. Dissolve 30 g of Zn(C2H3O2)2.2H2O in 3 g of 30% acetic acid and dilute to 50 ml. Mix the two solutions, add 50 mg of NaCl, allow to stand over night and filter.

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