REAGENTS AND SOLUTIONS 639 



double iodide solution and 750 c.c. of distilled water, making 5 liters 

 of solution. The 10 per cent NaOH should be made from a saturated 

 solution (containing about 55 gm. per 100 c.c.) which has been allowed 

 to stand until the carbonate has settled, the clear solution being de- 

 canted and used. This solution should have been standardized with 

 an accuracy of at least 5 per cent. 



(b) Formula of Bock and Benedict. Place 100 gm. mercuric iodide 

 and 70 gm. potassium iodide in a liter volumetric flask and add about 

 400 c.c. of water. Rotate until solution is complete. Now dissolve 

 100 gm. NaOH in about 500 c.c. of water, cool thoroughly and add 

 with constant shaking to the mixture in the flask, then make up with 

 water to the liter mark. This usually becomes perfectly clear. When 

 the small amount of brownish red precipitate which forms, settles out 

 the supernatant fluid is ready to be poured off and used. 



Neutral Olive Oil. 1 Shake ordinary olive oil with a 10 per cent 

 solution of sodium carbonate, extract the, mixture with ether, and 

 remove the ether by evaporation. The residue is neutral olive oil. 



Neutral Red. 2 A i per cent solution in 50 per cent alcohol. 



p-Nitrophenol. 2 A i per cent solution in 50 per cent alcohol. 



Nylander's Reagent. 3 Digest 2 grams of bismuth subnitrate 

 and 4 grams of Rochelle salt in 100 c.c. of a 10 per cent solution 

 of potassium hydroxide. The reagent should then be cooled and 

 filtered. 



Obermayer's Reagent. 4 Add 2-4 grams of ferric chloride to a 

 liter of hydrochloric acid (sp. gr. 1.19). 



Oxalated Plasma. 5 Allow arterial blood to run into an equal volume 

 of 0.2 per cent ammonium oxalate solution. 



Para-dimethylaminobenzaldehyde Solution. 6 This solution is 

 made by dissolving 5 grams of para-dimethylaminobenzaldehyde in 

 100 c.c. of 10 per cent sulphuric acid. 



Para-phenylenediamine Hydrochloride Solution. 7 Two grams dis- 

 solved in ico c.c. of water. 



Permutit. 8 A synthetic aluminium silicate obtained from the 

 Permutit Company, New York. Only such preparations as have 

 passed through a 60 mesh sieve and do not pass through an 80 mesh 

 sieve should be used. It should give off very little dust or turbid 



1 Einulsification of fats, p. 183. 



2 Determination of H ion concentration, pp. 161 and 501. 



3 Nylander's test, pp. 28 and 436. 



4 Obermayer's test, p. 405. 



5 Experiments on blood plasma, p. 271. 



6 Herter's para-dimethylaminobenzaldehyde reaction, p, 222. 



7 Detection of hydrogen peroxide, p. 341. 



8 Determination of ammonia and urea in urine, pp. 516 and 522. 



