358 



GIBBS. 



others have the opposite tendency. Yeij satisfactory standards are 

 prepared by dissolving a weighed quantity of pure methyl salicylate in 

 chloroform and carrying through the saponification in the same manner 

 as the determinations. Standards, representing from 1 to 2 milligrams 

 of methyl salicylate in 50 cubic centimeters of solution, have been found 

 to be most satisfactory for comparison with the wedge colorimeter. 



The solutions for analysis were prepared by agitating a large excess of pure 



methyl salicylate in water varying in purity from that of the usual laboratory 



distilled product to a conductivity of 2.8X10-* at 30°." As the rate of hydro- 



N 

 lysis of the ester in — sulphuric acid is under investigation, the solubility in 



this strength of acid has been determined from time to time as the hydrolysis 

 proceeds. 



In the following tables, No. is the number of the determinations, 

 T is the time expressed in hours during which the solutions were 

 agitated, S is the quantity of substance used in the determination, ex- 

 pressed in cubic centimeters, and Q is the methyl salicylate found in 

 solution and expressed as grams of solute in 100 cubic centimeters of 

 solvent. 



Table I. — SohihiUl)j of methyl salicylate in water (temperature, 30°). 



No. 



T 



. a 



Q 



1 



18 



5 



0.063 



2 



66 



10 



.069 



3 



139 



10 



.076 



4 



354 



10 



.076 



5 



834 



10 



.071 



6 



978 



5 



.074 



7 



2,160 



5 



.093 



8 



336 



5 



.074 



Determinations Nos. 1 to 6, inclusive, were made ujDon different 

 portions of the same solution, prepared by constantly agitating in a iDottle 

 10 cubic centimeters of nieth3d salicylate and 500 cubic centimeters 

 distilled water at 30° ±1°. No. 7 is the analysis of a mixture of 15 

 cubic centimeters of distilled water and 0.5 cubic centimeter of methyl 

 salicylate which had been agitated in a sealed glass tube for three months, 

 at temperatures varying from 30° to 100°. The system had approached 

 an equilibrium and the amount of methyl salicylate hydrolized was 

 found to be 0.0135 gram." No. 8 is the analvsis of a mixture of 10 



° In standardizing cells at 30°. I have used the temperature coefficients 

 found by Jones and West, Am. Chem. Jour. (1905), 34, 381. 



' This determination is not to be taken as an accurate measvire of the equili- 

 brium or the rate of hydrolysis for the reason that the action of the solutions 

 on the glass was found to be considej-able. A portion of the salicylic acid was 

 found to be present in the form of the sodium salt. 



