510 EXPERIMENT STATION RECORD. 



Other papers read were Varnishes on Chocolate and Confectionery, by B. H. 

 Smith (pp. 58-60) ; Suggested Modification of the Winton Lead Number, by 

 S. H. Ross (p. 58), previously noted (E. S. R., 22, p. 709) ; Phosphorus in 

 Flesh, by P. F. Trowbridge and Louise M. Stanley (pp. 158-160) noted else- 

 where (p. 512) from another source; Constants for Creatiuin Determinations, 

 by W. B. Smith and I, M. Myers (pp. 160-164) ; Occurrence of Methyl Pentosan 

 in Cattle Foods, by F. W, Morse (pp. 173-175) ; Dry Lead Defecation in Raw 

 Sugar Analysis, by W. D. Home (pp. 184-186) ; and Comparison of Methods for 

 Sucrose in Sugarhouse Control, by H. P. Agee (pp. 186, 187). 



The rate of solution ot casein, T. B. Robertson (Jour. Pliys. Chem., H 

 (1910), No. 5, pp. 377-392, figs. 2). — " If casein be stirred at an approximately 

 constant rate in solutions of the hydroxids of the allialis or of the alkaline 

 earths, the amount dissolved is connected with the time which has elapsed 

 since tlie casein was introduced into the solvent by the equation .r=Kt"', where 

 X is the number of grams of casein dissolved, t is the time, and K and Hi are 

 constants which depend upon the concentration and kind of hydroxid-solution 

 employed as solvent, and upon the total mass of casein in the mixture. 



"The rapidity of solution is, within the limits of the accuracy of the deter- 

 minations, unaffected by temperature, for temperatures ranging between room 

 temperature and 30°. Equally concentrated solutions of the hydroxids of 

 potassium, sodium, lithium, and ammonium dissolve casein at approximately the 

 same rate. Solutions of the hydroxids of the alkaline earths dissolve casein 

 much more lowly. Sr(OH)j dissolving it most rapidly, Ca(0H)2 more slowly, 

 and Ba(0H)2 more slowly still. The amount of casein dissolved by a solu- 

 tion of KOH in a given period of time is directly proportional to the concen- 

 tration of the KOH. 



" The rapidity with which casein is dissolved by a given solution of a 

 hydroxid of an alkali increases with the mass of casein present in the mixture. 

 At first the increase in the velocity of solution with increasing mass of casein 

 is rather large, but as the mass of casein is still further increased, the increase 

 in the rapidity of solution is less. 



"Having regard to the smallness of the temperature coefficient of this phe- 

 nomenon, to the dependence of the rate of solution upon the total mass of 

 casein present, and to the identity of the form of the equation x=Kt"'^ with 

 that which expresses the relation between the amount of a liquid absorbed by 

 a column of sand or a strip of filter paper and the time, it is suggested that the 

 factor which determines the rate of solution of casein in solutions of the hy- 

 droxids of the alkalis and of the alkaline earths may possibly be the velocity 

 with which the casein particles are penetrated and wetted by the solvent." 



See also previous notes (E. S. R., 10, p. 776: 20, p. 705). 



On the refractive indexes of solutions of certain proteins, T. B. Robertson 

 (Jour. Biol. Chem., 7 (1910), No. 5, pp. 359-36.',).— " The refractive indexes of 

 solutions of ovomucoid in distilled water are connected with their concentra- 

 tions by the formula : n—ni—aXc, where n is the refractive index of the solu- 

 tion, »i is the refractive index of the solvent, in this instance distilled water 

 (1.3333 at 18°), c is the percentage concentration of the protein in the solution, 

 and a is a constant which is numerically equal to the change in the refractive 

 index of the solvent which is brought about by dissolving 1 gm. in 100 cc. The 

 same law has previously been shown to hold good for solutions of casein in 

 various solvents. 



" The value of o. in the above formula, for ovomucoid is 0.00160. I-'or ovo- 

 vitellin the value of a is 0.00130. For casein the value of a has previously been 

 shown to be 0.00152." (See E. S. R., 22, p. 113.) 



