REAGENTS AND SOLUTIONS 631 



Black's Reagent 1 Made by dissolving 5 .grams of ferric chloride 

 and 0.4 gram of ferrous chloride in 100 c.c. of water. 



Blood Serum. This may easily be obtained in quantity by the 

 procedure described under Hemagglutination in the chapter on Blood. 



Boas' Reagent. 2 Dissolve 5 grams of resorcinol and 3 grams of 

 sucrose in 100 c.c. of 50 per cent alcohol. 



Buffer Solution. 3 (a) For Blood. Dissolve 69 gm. of mono- 

 sodium phosphate and 179 gm. of crystallized disodium phosphate in 

 800 c.c. of warm distilled water and dilute to one liter. 



(b) For Urine. Dissolve molecular proportions, 142 gm. Na2HP(>4 

 and 120 gm. NaH 2 PO 4 , or equivalent amounts of the crystalline salts 

 in enough water to make 1000 c.c. 



Carmine-Fibrin. 4 Prepared by running fibrin through a meat 

 chopper, washing carefully and placing in 0.5 per cent ammoniacal 

 carmine solution (very little excess ammonia should be present) until 

 the maximum coloration of the fibrin (dark red) is obtained. The fibrin 

 is then washed in water and in water acidified with acetic acid. It is 

 preserved under glycerol. 



Chloride Reagents for Blood Analysis. 5 (a) Standard Silver 

 Nitrate Solution. Dissolve 4.791 gm. of C. P. silver nitrate in distilled 

 water. Transfer this solution to a liter volumetric flask and make up 

 to the mark with distilled water. Mix thoroughly and preserve in a. 

 brown bottle, i c.c. = i nig. Cl. 



(b) Standard Thiocyanate Solution. As an approximation about 

 3 gm. of KCNS or 2.5 gm. of NH 4 CNS should be dissolved in a liter 

 of water. By titration under the conditions specified under "Pro- 

 cedure" (p. 285), and by proper dilution prepare a standard such that 

 5 c.c. are equivalent to 5 c.c. of the silver nitrate solution. 



(c) Ferric Ammonium Sulphate. The powdered salt is used. 

 Cochineal Solution. 6 A saturated solution of cochineal in 30 



per cent alcohol. 



Combined Hydrochloric Acid (Protein Salt). To prepare so-called 

 combined hydrochloric acid simply add a soluble protein such as Witte's 

 peptone to free hydrochloric acid of the desired strength until it no 

 longer responds to free acid tests (see chapter on Gastric Digestion). 

 For example, if 0.2 per cent combined acid is required the protein would 

 be added to 0.2 per cent free hydrochloric acid. 



1 Test for free acid, p. 156 



2 Black's reaction, p. 455. 



3 Determination of urea in blood p. 278 and urine p. 514. 



4 Tests on proteases, p. 12. 



5 Method of Whitehorn, p. 285. 



6 Determination of phosphates in urine, p. 568. 



