Odczynniki stosowane w chemii analitycznej – spis zawiera nazwy, zastosowanie i skład
Aluminon (qualitative tests for aluminium)
Aluminon is the trade name for the ammonium salt of aurin tricarboxylic acid. Dissolve 1 g of the salt in 1000 ml of distilled water. Shake the solution well to ensure thorough mixing.
Mix 1 part by volume of 55 % (m / m) nitric acid with 3 parts by volume of 32 / 33 % (v / v) hydrochloric acid.
Bang’s reagent (for glucose estimation)
Dissolve 100 g of K2CO3, 66 g of KCl and 160 g of KHCO3 in the order given above, in about 700 ml of water at 30 oC. Add 4,4 g CuSO4 and dilute to 1000 ml 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 1000 ml 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.
Benedict’s solution (qualitative test 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 g of CuSO4 x 5 H2O in 100 ml of water. Pour the latter solution, with constant stirring, into the carbonate citrate solution, and make up to 1000 ml .
Benzidine hydrochlorate solution (for sulphate determination)
Make a paste of 8 g of benzidine hydrochloride (C12H5(NH2)2 x 2 HCl) and 20 ml of water, add 20 ml of HCl (relative density 1,12) and dilute to 1000 ml with water. Each ml of this solution is equivalent to 3,57 mg of H2SO4.
Bertrand’s reagent (Glucose estimation)
Consists of the following solutions:
(1) Dissolve 200 g of Rochelle salts and 150 g of NaOH in sufficient water to make 1000 ml of solution.
(2) Dissolve 40 g of CuSO4 in enough water to make 1000 ml of solution.
(3) Dissolve 50 g of Fe2(SO4)3 and 200 g of H2SO4 (relative density 1,84) in sufficient water to make 1000 ml of solution.
(4) Dissolve 5 g of KMnO4 in sufficient water to make 1000 ml of solution.
Bial’s reagent (for pentose)
Dissolve 1 g of cresorcinol (CH3C6H3(OH)3) in 500 ml of 30 % HCl to which 30 drops of a 10 % of FeCl3 has been added.
Boutron-Boudet soap solution
(1) Dissolve 100 g of pure castile soap in about 2500 ml of 56 % ethyl alcohol
(2) Dissolve 0,59 g of Ba(NO3)2 in 1000 ml of water.
Adjust the castile soap solution so that 2,4 ml of it will give a permanent lather with 40 ml of the solution (2). When adjusted, 2,4 ml of soap solution is equivalent to 220 ppm of hardness (as CaCO3) for a 40 ml sample.
See also Soap solution.
Clarke’s soap solution (or A.P.H.A. standard method)
Estimation of hardness in water.
(1) Dissolve 100 g of pure powdered castile soap in 1000 ml of 80 % ethyl alcohol and allow to stand overnight.
(2) Prepare a standard solution of CaCl2 by dissolving 0,5 g of CaCO3 in HCl (relative density 1,19), neutralise with NH4OH and make slightly alkaline to litmus, then dilute to 500 ml. One ml is equivalent to 1mg of CaCO3.
Titrate (1.) against (2.) and dilute (1.) with 80 % ethyl alcohol until 1 ml of the resulting solution is equivalent to 1 ml of (2.) after making allowance for the lather factor (the amount of standard soap solution required to produce a permanent lather in 50 ml of distilled 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 K3Co(CN)6 and 1 g of KCIO3 in 100 ml water. Soak filter paper in the solution and dry at 100 oC. Apply a drop of zinc solution and burn in an evaporating dish. A green disc is obtained if zinc is present.
Extract 1 g of cochineal for four days with 20 ml of alcohol and 60 ml of distilled water. Filter.
Dissolve 0,5 g of congo red in 90 ml of distilled water and 10 ml of alcohol.
Cupferron (Baudisch’s reagent or iron analysis)
Dissolve 6 g of the ammonium salt of nitroso-phenyl-hydroxylamine (cupferron) in 100 ml of water. Reagent good for one week only and must be kept in the dark.
Cupric acetate (Barfoeds reagent for reducing mono-saccaharides)
Dissolve 66 g of cupric acetate and 10 ml of glacial acetic acid in water and dilute to 1 litre.
Cupric oxide, ammoniacal, Schweitzer’s reagent (dissolves cotton, linen and silk, but not wool)
Dissolve 5 g of cupric sulphate 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. 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 sulphate in glycerin-potassium hydroxide (reagent for silk)
Dissolve 10 g of cupric sulphate CuSO4 x 5 H2O in 100 ml of water and add 5 g of glycerin. Add KOH slowly until a deep blue solution is obtained.
Cupron (Benzoin oxime)
Dissolve 5 g in 10 ml of 95 % alcohol.
Cuprous Chloride, acidic (reagent for CO in gas analysis)
Method 1: Cover the bottom of a 2 litre flask with a layer of cupric oxide about 10 to 15 mm deep, suspend a bunch of copper wire so as to reach from the bottom to the top of the solution, and fill he flask with hydrochloric acid (relative density 1,10). Shake occasionally. When the solution becomes nearly colourless, transfer the reagent bottles, which should also contain wire. The stock bottle may be refilled with dilute hydrochloric acid until either the cupric oxide, or the copper wire is used up. Copper sulphate may be substituted for copper oxide in the above procedure.
Method 2: Dissolve 340 g of CuCl2 x 2 H20 in 600 ml of conc HCl and reduce the cupric chloride by adding 190 ml of saturated solution of stannous chloride or until the solution is colourless. 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.
(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 colourless, it is ready to use.
Cuprous chloride, ammoniacal (reagent for CO in gas analysis)
The acid solution of cuprous chloride as prepared above is neutralised with ammonium hydroxide until an ammonia odour persists. An excess of metallic copper must be kept in solution.
Pour 800 ml of acidic cuprous chloride, prepared by the Winkler method, into about 4 litres of water. Transfer the precipitate to a 250 ml graduated flask. 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 shaken and allowed to stand for several hours. It should have a faint odour of ammonia.
Dissolve 1 g in 1 litre of 70 % alcohol or 1 g of the sodium salt in 1 litre of water.
Diphenylamine (reagent for rayon)
Dissolve 0,2 g Diphenylamine in 100 ml of concentrated sulphuric acid.
Diphenylamine sulphonate (for titration of iron with K2Cr2O7)
Dissolve 0,2 g of diphenylcarbazide in 10 ml of glacial 500 ml of 95 % ethyl alcohol. This is an especially sensitive test for nickel, a very definite crimson colour being produced.
Copper sulphate solution
Dissolve 34,66 g of CuSO4 x 5 H20 in water and dilute to 500 ml.
Alkaline tartrate solution
Dissolve 173 g of potassium sodium tartrate (Rochelle salts, KNaC4H4O6 x 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.
Dissolve 140 g of ferric-ammonium sulphate crystals in 400 ml of hot water. When cool, filter, and make up to a volume of 500 ml with dilute (6N) nitric acid
Folins 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 one litre.
Formaldehyde-sulphuric acid (Maquis reagent or alkaloids)
Add 10 ml of formaldehyde solution to 50 ml of sulphuric acid.
See Sulphomolybdic acid.
Fuchsin (reagent for linen)
Dissolve 1 g of fuchsin in 100 ml of alcohol.
Fuchsin-sulphurous acid (Schiff’s reagent for aldehydes)
Dissolve 0,5 g of fuchsin and 9 g of bisulphite in 500 ml of water, and add 10 ml of HCl. 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.
See Picric acid.
Hanus solution (or iodine number)
Dissolve 13,2 g of resublimed iodine in 1 litre of glacial 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 1 litre with alcohol
Iodo-potassium iodide (Wagner’s reagent of alkaloids)
Dissolve 2 g of iodine and 6 g of KI in 100 ml of water.
Extract litmus powder three times with boiling alcohol, each treatment consuming an hour. Reject the alcohol extract. Treat residue with an equal mass of cold water and filter; then exhaust with 5 times its mass 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 litre. The ammonium hydroxide may be omitted until just previous to use. The reagent, if completely mixed and stored for any length of time becomes turbid.
See S and O reagent.
Magnesium uranyl acetate
Dissolve 100 g of UO2(C2H3O2)2 x 2 H2O in 60 ml of glacial acetic acid and dilute to 500 ml. Dissolve in 330 g of Mg(C2H3O2)2 x 4 H2O 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 the uranyl solution, cool and dilute to 1 litre. Let stand and filter if necessary
See potassium-cadmium iodide.
See Formaldehyde-sulphuric acid.
Mayer’s reagent (white precipitate with most alkoids in slightly acid solutions)
Disslove 1,358 g of HgCl2 in 60 ml of water and pour into solution of 5 g of KI in 10 ml of H2O. Add sufficient water to make 100 ml.
Methyl orange indicator
Disslove 1 g of methyl orange in 1 litre of water. Filter if necessary.
Methyl orange, modified
Dissolve 2 g of methyl orange and 2,8 g of xylene cyanol FF in 1 litre 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 1,23 g of xylene cyanol FF in 1 litre of 90 % alcohol.
Or, dissolve 1,25 g of methyl red and 0,825 g of methylene blue in 1 litre of 90 % alcohol.
Million’s reagent (the 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.
Prepared by adding about 1,4 g of xylene cyanole FF to 1 g of methyl orange. The dye is seldom pure enough for these proportions to be satisfactory. Each new lot of dye should be tested by adding additional amounts of the dye until a test portion shows the proper colour change The acid colour of this indicator is like that of permanganate, the neutral colour is grey; and the alkaline colour is green. Described by Hickman and Linstead, J.Chem. Soc (Lon),121 2502 (1922).
α-Natpthol (Molish’s reagent for wool)
Dissolve 15 g α-napthol in 10 ml of alcohol or chloroform
Nessler’s reagent (for ammonia)
Dissolve 50 g of KI in the smallest possible quantity of cold water (about 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 litre. Let settle, and draw off the clear liquid.
Nickel oxide, ammoniacal (reagent for silk)
Dissolve 5 g of nickel sulphate 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.
p-Nitrobenzene-azo-resorcinol (reagent for magnesium)
Dissolve 1 g of the dye in 10 ml of 1 N NaOH and dilute to 1 litre.
Nitron (detection of nitrate radical)
Dissolve 10 g of nitron (C20H16N, chemical name 4,5-dihydro-1,4-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.
Make a saturated solution in 50 % acetic acid (one part of glacial acetic acid with one part of water). Does not keep well.
Dissolve 20 g of bismuth subnitrate and 40 g of Rochelle salts in one litre of 8 % NaOH solution. Cool and filter.
Obermayer’s reagent (for indoxyl in urine)
Dissolve 4 g of FeCl3 in one litre of HCl (relative density 1,19).
Dissolve 14 g of C9H7ON (= 8-Hydroxyquinoline) in 30 ml of glacial acid. Warm slightly, if necessary. Dilute to one litre.
Dissolve 300 g of ammonium chloride in one litre of water and add 1 litre 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 NH4Cl-NH4OH solution and the gas passed through.
Pasteur’s salt solution
To one litre of distilled water add 2,5 g of potassium phosphate, 0,25 g of calcium phosphate, 0,25 g of magnesium sulphate and 12,00 g of ammonium tartrate.
Pavy’s solution (glucose reagent)
To 120 ml of Fehling’s solution add 300 ml of NH4OH (relative density 0,88) and dilute to one litre with water.
Phenanthroline ferrous ion indicator
Dissolve 1,485 g of phenanthroline monohydrate in 100 ml of 0,025 M ferrous sulphate solution
Dissolve 1 g of phenolphthalein in 50 ml of alcohol and add 50 ml of water
Phenolsulphuric acid (determination of nitrogen as nitrates)
Dissolve 25 g of phenol in 150 ml of conc. H2SO4 add 75 ml of fuming H2SO4 (15 % SO3), stir well and heat for two hours at 100 oC.
Phloroglucinol solution (pentosans)
Make a 3 % phloroglucinol solution in alcohol. Keep in a dark bottle.
Phosphomolybdic acid (Sonnenschein’s reagent for alkaloids)
Method 1: Prepare ammonium phosphomolybdate and after washing with water, boil with nitric acid and expel NH3; evaporate to dryness and dissolve in 2N nitric acid
Method 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 Sonnensheins reagent.
Phosphoric acid – sulphuric acid mixture
Dilute 150 ml of conc. H2SO4 and 100 ml of conc. H3PO4 (85 %) with water to a volume of one litre.
Phosphotungstic acid (Scheibler’s reagent for alkaloids)
Dissolve 20 g of sodium tungstate and 15 g of sodium phosphate in 100 ml of water containing a little nitric acid.
The reagent is a 10 % solution of phosphotungstic acid in water. The phosphotungstic acid is prepared by evaporating a mixture 10 g of sodium tungstate dissolved in 5 g of phosphoric acid (relative density 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.
Potassium antimonite (reagent for sodium)
Boil 22 g of potassium antimonate with 1000 ml of water until nearly all of the salt has dissolved, cool quickly, add 35 ml of 10 % potassium hydroxide. Filter after standing overnight.
Potassium–cadmium iodide (Marme’s reagent for alkaloids)
Add 2 g of CdI2 to a boiling solution of 4 g of KI in 12 ml of water, and then mix with 12 ml of saturated KI solution.
Potassium hydroxide (for CO2 absorption)
Dissolve 360 g of KOH in water and dilute to 1000 ml.
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 1 litre
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.
(1) Dissolve 75 g of pyrogallic acid in 75 ml of water.
(2) Dissolve 500 g of KOH on 250 ml of water. When cool, adjust until relative density is 1,55.
For use, add 270 ml of solution (2.) to 30 ml of solution (1.)
Rosolic acid (indicator)
Dissolve 1 g of rosolic acid in 10 ml of alcohol and add 100 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 N NaOH.
See Phosphotungstic acid.
See Fuchsin-sulphurous acid
See Cupric oxide, ammoniacal.
Soap solution (reagent for hardness in water)
Dissolve 100 g of dry castile soap in 1000 ml of 80 % alcohol (5 parts of alcohol to 1 part of water). Allow to stand several days and dilute with 70 % to 80 % alcohol until 6,4 ml produces a permanents 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 1000 ml.
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 1000 ml.
Sodium nitroprusside (reagent for hydrogen sulphide 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 commercial salt in 1000 ml 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 sulphate and is neutral to phenolphthalein.
Sodium plumite (reagent for wool)
Dissolve 5 g of sodium hydroxide in 100 ml of water. Add 5 g of litharge and boil until dissolved.
Dissolve 480 g of Na2S x 9 H2O in 500 ml of water, add 400 g of NaOH and 18 g of sulphur. Stir thoroughly and dilute to 1000 ml with water.
See Phosphomolybdic acid.
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 1000 ml 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.
A solution of starch which keeps indefinitely is made as follows: Mix 500 ml of saturated NaCl solution (filtered), 80 ml of glacial acetic acid, 20 ml of water and 3 g of starch. Bring slowly to the boil and boil for two minutes.
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 4 g 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.
Dissolve 30 g of FeSO4 and 20 g of tartaric acid in water and dilute to 1000 ml. Just before using, add concentrated NH4OH until the precipitate first formed is redissolved.
Sulphanilic acid (reagent for nitrates)
Dissolve 0,5 g of sulphanilic acid in a mixture of 15 ml of glacial acetic acid and 135 ml of recently boiled water.
Sulphomolybdic 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 albument, alkaloids and gelatin)
Dissolve 10 g of tannic acid in 10 ml of alcohol and dilute with water to 100 ml.
See Zimmermann-Reinhardt reagent.
o-Tolidine solution (residual chlorine in water analysis)
Prepare 1000 ml of dilute HCl (100 ml of HCl (relative density 1,19) in sufficient water to make 1000 ml). Dissolve 1 g of o-tolidine in the 100 ml of the dilute HCl and dilute to 1000 ml with the dilute HCl solution. (This reagent is carcinogenic)
See Picric acid.
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 for several days with six times its mass of alcohol. Filter.
Uffelmann’s reagent (turns yellow in presence of lactic acid)
To a 2 % solution of pure phenol in water, add a solution of FeCl3 until the phenol solution becomes violet in colour.
See iodo-potassium iodide.
Wagner’s solution (used in phosphate rock analysis to prevent precipitation of iron and aluminium)
Dissolve 25 g of citric acid and 1 g salicylic acid in water and dilute to 1000 ml. Use 50 ml of the reagent.
Wij’s iodine monochloride solution (for iodine number)
Dissolve 13 g of resublimed iodine in 1000 ml 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 (relative density 1,84) until the characteristic odour 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-coloured 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 (p-toluene-sulfonedichloroamine), and 16,6 g of dry KI (in small quantities with continual shaking until all the KI has dissolved). Make up to 1000 ml with the same quality of acetic acid used above and preserve in a dark coloured bottle.
Zimmermann-Reinhardt reagent (determination of iron)
Dissolve 70 g of MnSO4 x 4 H2O in 500 ml of water, add 125 ml of conc H2SO4 and 125 ml of 85 % H3PO4 and dilute to 1000 ml.
Zinc chloride solution (reagent for silk)
Dissolve 100 g of zinc chloride in 85 ml of water, and add 4 g of zinc oxide. Heat until solution is complete.
Zinc uranyl acetate (reagent for sodium)
Dissolve 10 g of UO2(C2H3O2)2 x 2 H2O in 6 g of 30 % acetic acid with heat, if necessary, and dilute to 50 ml. Dissolve 30 g of Zn(C2H3O2)2 x 2 H20 in 3 g of 30 % acetic acid and dilute to 50 ml. Mix the two solutions, add 50 mg of NaCl, allow to stand overnight and filter.