9 

 24 INFLUENCE OF FOOD PEESERVATIVES ON HEALTH. 



tion of water and phosphoric acid, the determinations were made as 

 described under food. 



The phosphoric acid was determined by the uranium acetate vol- 

 umetric method, a the only modification in the method given by Sutton 

 being that the urine was diluted with 2 volumes of water. This was 

 found to be advisable for two reasons: First, to reduce the color, which 

 otherwise interfered to some extent with the end reaction; second, 

 because of the large amount of phosphoric acid present, which was 

 found to be too great for exact results. The solids were determined 

 by multiplying the specific gravity minus 1 (at 25) by the factor 2450, 

 or, as it is. more commonly expressed, by multiplying the last three 

 figures of the specific gravity (expressed as a whole number where the 

 result is entered in four decimals) by 0.245. This factor is consider- 

 ably higher than th Q t which has ordinarily been employed (0.233). It 

 was the result of considerable experimental work on the part of Mr. 

 Weber, who conducted the urine analyses, and it is not greatly differ- 

 ent from the results obtained by Long. The clinical examination of 

 the urine was made by Mr. F. C. Weber. 



In addition to the determinations previously mentioned, boric acid 

 was determined in the urine. The method employed was that of 

 Thompson. 6 During a portion of the time barium hydroxid was 

 substituted for calcium hydroxid, and the barium precipitate was dis- 

 solved in hydrochloric acid and reprecipitated to free the last portions 

 of boric acid from the precipitate. Comparative experiments were 

 also made with methods involving distillation with methyl alcohol, 

 but on the whole Thompson's method was found to be the most satis- 

 factoiy, both on account of its greater convenience and because of the 

 large amount of soluble salts present, which tended to interfere with 

 the accuracy of the distillation method. The determinations of boric 

 acid on the first series were made by Mr. W. D. Bigelow, and on the 

 second, third, fourth, and fifth series by Mr. J. S. Burd. 



ANALYSIS OF FECES. 



The feces were collected in a can contrived for that purpose, and 

 dried in a current of air at the temperature of boiling water. The 

 can employed is shown in the accompanying illustration in its place in 

 the apparatus, a cross-section view (a) also being given. It is 5 inches 

 high and 5f inches in diameter, closed with a friction top. Its con- 

 struction is based upon the principle that with a beveled top fitting 

 into an even opening a practically air-tight union can be secured. 

 These cans are similar in their construction, so far as the opening is 

 concerned, to those commonly used for holding paints. 



In order that the same can in which the feces were collected might 



a Button's Volumetric Analysis, eighth edition, page 436. 

 & Button's Volumetric Analysis, eighth edition, page 98. 



