614 EXPERIMENT STATION EECOED. [Vol.35 



about 1 iBi,'. of barium sulphate. The final volume of the solution after pre- 

 cipitating the sulphate should thus be about 250 to .350 cc. After oxidizing a 

 suitable aliquot with sodium peroxid, heating to hasten the oxidation, and 

 acidifying, the solution should be boiled to drive out dissolved gases, exactly 

 neutralized, and an amount of concentrated hydrochloric acid added so that 

 the volume percentage of hydrochloric acid does not exceed 2 per cent. After 

 diluting the acidified solution to the proper volume it is heated to boiling and 

 precipitated hot with 20 cc. of 5 per cent barium chlorid added from a burette 

 at the rate of from 5 to 10 cc. per minute, preferably at the slower rate. The 

 solution should not be shaken or stirred. The beaker and contents after the 

 precipitant has been added are set aside and allowed to stand for at least 

 12 hours before filtering. After filtration the precipitate is washed with cold 

 water until free from chlorids, using a uniform quantity of wash water, 

 150 cc. added in 15 cc. portions usually sufficing to free a precipitate of this size 

 f7-om chlorids, and introducing a negligible loss due to solubility of barium 

 sulphate. 



In an attempt to increase the knowledge of the mechanism of the reaction 

 other precipitants for sulphur were tried. The authors conclude that they 

 have no better explanation for the mechanism of the reaction than those offered 

 by earlier investigators. The necessity for following a definite set of conditions 

 in sulphur analysis is strongly emphasized. 

 A list of 43 references cited is appended. 



The quantitative determination of the total protein and nonprotein sub- 

 stances of muscle. Improved technique, N. W. Janney {Jour. Biol. Chem., 

 25 {1916), No. 2, pp. 177-183). — The following modified quantitative procedure 

 is outlined : 



" The fresh muscle is freed from all adherent fat and connective tissue, 

 passed through a meat grinder, and thoroughly mixed. About 10 gm. is weighed 

 by difference into a beaker from a weighing glass provided with a ground glass 

 lid. Fifty cc. of 95 per cent alcohol is added and the contents of the beaker 

 heated, with stirring, until the alcohol boils. The liquid is then decanted 

 through an ordinary round filter of 12.5 cm. diameter, which has previously 

 been extracted with alcohol and ether, dried, and weighed. This treatment of 

 the protein with alcohol is once repeated. 



" The coagulated muscle is next extracte<l in a similar manner with 400 cc. 

 of boiling water in four portions, and then brought quantitatively on the filter. 

 The filter is now carefully folded about the protein material, which is gently 

 inserted into an extraction hull and extracted three hours in an ordinary 

 Soxhlet apparatus with 95 per cent alcohol. The 95 per cent alcohol is then 

 replaced by absolute alcohol and the extraction continued for a period of 

 15 hours. Care must be taken that the filter projects beyond the upper level 

 attainable by the solvent, which must completely surround the protein. After 

 completion of the extraction the filter with the pure protein is removed from 

 the apparatus, dried to cortstant weight at 105° [C.j in a weighing glass provided 

 with a ground glass lid, and the previously ascertained weight of the filter paper 

 deducted." 



When required, the nonprotein substances are determined by deducting the 

 percentage of protein found from the percentage of total solids. 



The protein content of muscle, N. W. Ja-Nney {Jour. Biol. Chem., 25 {1916), 

 No. 2, pp. 185-1S8). — This material has been essentially noted from another 

 source (E. S. R., 3.5, p. 315). 



The ninhydrin reaction with amino acids and ammonium salts, V. J. 

 Harding and h\ H. S. Wabnefoed {Jour. Biol. Chem., 25 {1916), No. 2, pp. 319- 



