29 



application of tbis test to commercial gelatin the following process was 

 employed. 



Fifty grams of commercial gelatin were dissolved in warm water and 

 the solution diluted to half a liter. In 10 cc of this solution, corre- 

 sponding to 1 gram of the gelatin, the nitrogen is determined directly 

 by the Gunning-Kjeldahl process. Another portion of 10 cc is treated 

 with an excess of bromin in the following manner. 



The solution is first brought to a volume of 100 cc with water and 

 placed in a conical beaker with a sufficient quantity of hydrochloric 

 acid to produce distinct acid reaction. A saturated solution of bromin 

 water is added in considerable excess, and the liquid stirred vigorously 

 for some time. The precipitate which separates is flocculent when first 

 formed, but becomes more viscous after stirring and adheres for the 

 most part to the sides of the beaker, which, with its contents, is allowed 

 to stand for about half an hour, or until all the precipitate is settled. 

 The supernatant liquor is decanted through an asbestus filter. The 

 precipitate adhering to the beaker is washed several times with cold, 

 distilled water and the washings poured through the filter. Occasion- 

 ally, when most of the free broniiu is washed out of the precipitate, the 

 liquid does not filter clear. It is therefore advisable to keep the wash- 

 ings separated from the filtrate, and, if necessary, wash with sodium- 

 sulphate solution or with bromin water. The nitrogen in the precipitate 

 is determined by the Gunning-Kjeldahl process as follows: 



The precipitate which has been collected on the asbestus filter, together 

 with the asbestus, is returned to the beaker in which the precipitation 

 took place. Twenty cubic centimeters of strong sulphuric acid are 

 added, the beaker covered with a watch glass and placed on a wire 

 gauze over a lamp. When frothing has ceased, about 10 grains of pow- 

 dered potassium sulphate are added and the liquid boiled until color- 

 less. After cooling it is distilled with water and the ammonia distilled 

 off and determined in the usual way. . The percentage of nitrogen found, 

 when multiplied by the factor 6.3:>, or in the case of gelatin by 5.5, gives 

 the amount of proteid matter precipitated by bromin. In the commer- 

 cial gelatin above mentioned the nitrogen content was found to be 14.1 

 and 14 per cent, respectively, on two determinations. Solutions of 

 kreatinin, asparagin. and aspartic acid were found to yield no precipi- 

 tates with bromiu, but brotnin was found to precipitate all albumin, 

 acid albumin, and all peptones formed by the digestion of albumin with 

 pepsin. 



APPLICATION TO COMMERCIAL MEAT EXTRACTS. 



On applying the bromin method to commercial meat extracts the 

 following results were obtained. The solutions of the Bovril prepara- 

 tions were not previously filtered, and therefore the figures contain the 

 nitrogen and the fiber present. 



