. Essentials of laboratory diagnosis; designed for students and practitioners. he end of this timethe bell-jar is removed, the acid titrated with tenth-normalsodium hydrate, and the number of cubic centimeters of re-maining acid determined. One cubic centimeter of tenth-nor-mal sulphuric acid neutralized by the evolved ammonia repre-sents gram of ammonia. This figure is multiplied by4 to obtain the percentage ammonia value. If any moisture ispresent on the inside of the bell-jar it should be washed into thesulphuric acid before 5 Websters Diagnosis. 6 Ibid. AMMONIA. 257 Fo
. Essentials of laboratory diagnosis; designed for students and practitioners. he end of this timethe bell-jar is removed, the acid titrated with tenth-normalsodium hydrate, and the number of cubic centimeters of re-maining acid determined. One cubic centimeter of tenth-nor-mal sulphuric acid neutralized by the evolved ammonia repre-sents gram of ammonia. This figure is multiplied by4 to obtain the percentage ammonia value. If any moisture ispresent on the inside of the bell-jar it should be washed into thesulphuric acid before 5 Websters Diagnosis. 6 Ibid. AMMONIA. 257 Formalin Method.—This method, originated by Roncheseand Malfatti, depends on the fact that a solution of an am-monium salt, treated with formaldehyde decomposes with theformation of hexamethylenetetramin, the acid combined withthe ammonia being liberated. This can then be determined bytitration. Dilute 10 cubic centimeters of urine with 50 cubic centi-meters oi water, add 2 or 3 drops of a 1 per cent, alcoholic solu-tion of phenolphthalein, and neutralize with ~- NaOH. Five. Fig. 43.—Folins Ammonia Apparatus. cubic centimeters of formalin, previously neutralized with ~^-]STaOH, are added to the neutralized urine and the mixture is again titrated with NaOH to the appearance of a faintpermanent pink color, the amount of alkali used being noted. Itis evident that 1 cubic centimeter of this -^ NaOH is equiva- cubic centimeter of ~ NII3, or, in other words, lent to 1 represents gram of NH3. Multiply the number ofcubic centimeters of -^ NaOH used by this factor to obtainthe NH3 in 10 cubic centimeters of urine. Caution.—It has been found that formalin combines, also,with the NH2 group of the amino-acids, thus leading to resultshigher than those of the Folin method. If the figure obtained 17 258 THE URINE. by the Folin method be subtracted from that of the formalinmethod, the result is the NH2 referable to amino-acids. Folins Method.—This method, while giving most accur
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