39 APPENDIX. 



Benzidine hydrochloride, see p. 357. 



Bromine water, saturated. Made by shaking bromine with cold distilled 

 water. 



Brucke's reagent, see p. 37. 



Calcium chloride, normal. 55-5 grams, pure anyhdrous CaCl 2 , dissolved in 

 water, made up to i litre and filtered. One-fifth normal is a convenient 

 strength for certain exercises. 



Charcoal, adsorbent. The author has found that certain samples of the 

 charcoal prepared by the Chemical Warfare Department for filling protective 

 gasmasks are highly efficient, being superior to Merck's "blood charcoal." 

 It is hoped that carefully selected supplies will shortly be obtainable from 

 Messrs. Baird and Tatlock's and other dealers. 



Chromic acid cleaning fluid. Ten per cent, of chromic acid in water, or 

 10 per cent, of potassium bichromate dissolved in 10 percent, (by volume) 

 of sulphuric acid. 



Cochineal tincture, see p. 354. 

 Collodion solution, see p. 3. 



Congo red paper. White filter paper is thoroughly wetted with a 0-2 per 

 cent, solution of congo red in water. The paper is pinned up till dry and cut 

 into strips. It is turned blue by strong acids. 



Copper sulphate. 200 grams, of pure crystalline CuSO 4 .5H 2 O are dissolved 

 in distilled water by the aid of heat, cooled and made up to i litre. For the 

 biuret reaction a i per cent, solution is prepared by diluting 5 cc. to 100 cc. 



Ehrlich's reagent for indol. Para-dimethyl-amido-benzaldehyde 4 parts 

 Alcohol (95 to 98 per cent.) . . 380 ,, 

 Concentrated hydrochloric acid 80 ,, 



Esbach's reagent, see p. 36. 

 Fehling's solution, see p. 106. 

 Ferric chloride, 10 per cent. 

 Glyoxylic reagent, see p. 39. 



Grease paint, for marking beakers, etc. Dilute Brunswick Black to the 

 desired consistency with naphtha or benzene. Apply with a fine brush. Can 

 be scraped off or removed by means of a pad of cotton wool soaked in naphtha. 



Gunzberg's reagent. Dissolve 2 grams, phloroglucin and i gram, of 

 vanillin in 30 cc. of absolute alcohol. The solution should be freshly 

 prepared, but it can be preserved for a certain time in dark bottles. 



Ink for writing on glass. 



A. 13 per cent, solution of shellac in strong alcohol. 



B. 13 per cent, solution of borax in distilled water. 



Mix 3 parts of A with 5 parts of B, and add some stain in alcoholic or aqueous 

 solution. 



Iodine solution. About o-i N. Dissolve 25 grams, of potassium iodide in 

 about 200 cc. of distilled water in a stoppered flask. Add 12-7 grams, of iodine 

 and shake till dissolved. Make up to i litre with distilled water. For many 

 purposes this can be diluted 10 times or even more with distilled water, but 

 these weak solutions should be prepared as required. 



Lead acetate (basic). Boil 464 grams, of normal lead acetate and 264 

 grams, of litharge in 1500 cc. of distilled water for half an hour with constant 

 stirring. Cool and filter. Or use a saturated solution of the commercial 

 basic lead acetate. 



