638 PHYSIOLOGICAL CHEMISTRY 



Methyl Orange. 1 Dissolve o.i gm. of methyl orange in 100 c.c. of 

 distilled water. 



Millon's Reagent. 2 Digest i part (by weight) of mercury with 

 2 parts (by weight) of nitric acid (sp. gr. 1.42) and dilute the resulting 

 solution with 2 volumes of water. 



Molisch's Reagent 3 A 15 per cent alcoholic solution of a-naphthol. 



Molybdate Solution. 4 Dissolve 100 grams of molybdic acid in 144 

 <:.c. of ammonium hydroxide (sp. gr. 0.90) and 271 c.c. of water; slowly 

 and with constant stirring pour the solution thus obtained into 489 c.c. 

 of nitric acid (sp. gr. 1.42) and 1148 c.c. of water. Keep the mixture in 

 a warm place for several days, or until a portion heated to 40 C. deposits 

 no yellow precipitate of ammonium phosphomolybdate. Decant the 

 solution from any sediment and preserve in glass-stoppered bottles. 



Morner's Reagent. 5 - Thoroughly mix i volume of formalin, 45 

 volumes of distilled water, and 55 volumes of concentrated sulphuric 

 acid. 



a-Naphthol Solution. 6 Dissolve i gram of a-naphthol in 100 c.c. of 

 95 per cent alcohol. 



Nessler's Reagent. 7 (a) Formula of Folin and Wu. Nessler's 

 solution is an alkaline solution of the double iodide of mercury and 

 potassium (HgI 2 2KI). Introduce into a 500 c.c. Florence flask 

 150 gm. potassium iodide and no gm. of iodine; add 100 c.c. of water 

 and an excess of metallic mercury, 140-150 gm. Shake the flask 

 continuously and vigorously for 7-15 minutes or until the dissolved 

 iodine has nearly all disappeared. The solution becomes quite hot. 

 When the red iodine solution has begun to become visibly pale, though 

 still red, cool in running water and continue the shaking until the 

 reddish color of the iodine has been replaced by the greenish color of 

 the double iodide. The whole operation does not usually take more 

 than 15 minutes. Decant the solution, washing mercury and flask 

 with liberal quantities of distilled water. Dilute solution and washings 

 to 2 liters. - If the cooling was begun in time the resulting reagent is 

 clear enough for immediate dilution with 10 per cent alkali and water 

 and the finished solution can be used at once for Nesslerization. From 

 this stock solution of potassium mercuric iodide prepare final Nessler's 

 solutions as follows: Introduce into a flask of at least 5 liters capacity, 

 3500 c.c. of 10 per cent sodium hydroxide solution, add 750 c.c. of the 



1 Determination of urea in urine, p. 518. 



2 Millon's reaction, p. 97. 



3 Molisch's reaction, p. 21. 



4 Detection and determination of phosphorus, pp. 128 and 571. 



6 Morner's test, p. 85. 



8 Oxidases p. 15. For other a-naphthol solution see Molisch reaction. 



7 Determination of nitrogen pp. 278, 279 and 508. 



