METHODS OF ANALYSIS. 43 



Association of Official Agricultural Chemists a for the determina- 

 tion of glycerol in wines, and Lane's method, 6 as well as numerous 

 extraction methods. Among the solvents used were benzol, amyl- 

 acetate, gasoline, carbon tetrachlorid, carbon bisulphid, and acetone. 

 All of these solvents extract varying amounts of meat bases, or 

 extractives, and give different results on the glycerol present. The 

 following reagents were used to precipitate the dissolved meat bases: 

 Lead acetate, silver nitrate, and phosphotungstic acid. The best 

 results were obtained by extracting with acetone, the meat bases 

 being precipitated first with silver nitrate, lollowed by phospho- 

 tungstic acid. The glycerol in the filtrate was estimated by the 

 Hehner c method. 



Shukoff and Shestakoff d describe an acetone extraction method, 

 but weigh the glycerol, and it is impossible to estimate this bod}" in 

 the case of meat extracts by weighing on account of the salts and 

 extractives dissolved by the acetone and weighed as glycerol. 



A method using anhydrous copper sulphate and extracting with 

 acetone is now under investigation. 



NITRATES. 



A qualitative test for nitrates was made in 28 samples of meat 

 extracts, meat peptones, fluid meat juices, and fluid extracts. The 

 samples were collected in July, 1907, and in general represent the 

 same brands as were used in the other studies. 



The diphenylamin e test was used. The reagent was made by 

 dissolving 1 part of diphenylamin in 100 parts of concentrated sul- 

 phuric acid. The test was applied as follows: 



Transfer 1.5 grams of the semisolid, or 1 cc of the liquid extracts, 

 to a 250 cc beaker and boil with animal charcoal for two or three 

 minutes. Filter the solution hot and test one drop of the filtrate 

 on a porcelain plate with three drops of the diphenylamin reagent. 

 A blue color indicates nitrates, and the depth of color shows in a 

 general way the amount of nitrates present. 



Negative tests for nitrates were obtained in the case of 14 of the 

 28 samples examined. The results on the 14 samples giving posi- 



o U. S. Dept. Agr., Bureau of Chemistry, Bui. 107, p. 83. 



b Unpublished. The method reads as follows: 



Precipitate a known weight or volume with basic lead acetate, make, up to a known 

 volume with alcohol, filter, take an aliquot part, add a little anhydrous lime, distil 

 nearly to dryness in a steam bath (keep the flask immersed), add an excess of anhy- 

 drous CaO, mix, moisten with alcohol to facilitate mixing if necessary, distil again 

 on steam bath to combine water with CaO, and extract with two-thirds alcohol and 

 one-third chloroform, as usual. 



cj. Soc. Chem. Ind., 1889. 8:4. 



*Zte. angew. Chem., 1905, 18:294. 



eArch. Hyg., 1884, 2:373. 



