Issued February 2, 1910. 



UNITED STATES DEPARTMENT OF AGRICULTURE, 



BUREAU OF CHEMISTRY Circular No. 50. 

 H. W. WILEY, Chief of Bureau. 



THE QUANTITATIVE DETERMINATION OF CANE SUGAR BY THE 

 USE OF INVERTASE. 



By C. S. HUDSON, Assistant Chemist. 

 INTRODUCTION. 



The general method now in use for estimating cane sugar is that of 

 Clerget, in which the sugar is hydrolyzed by acid and the resulting 

 invert sugar estimated either by its reduction of Feh ling's solution or 

 by the change in optical rotation which results from the hydrolysis. 

 It has long been known that the presence of other hydrolyzable sub- 

 stances with the cane sugar interferes in the determination because 

 the hydrolysis by acid is then not confined to the cane sugar. This 

 method would be greatly improved if some substitute for the acid 

 were known which would hydrotyze the cane sugar without attacking 

 other acid-hydrolyzable substances; it is the purpose of this article to 

 show that the enzym invertase in most cases fulfils this requirement, 

 and that its use to supplement or even replace acids in the quantitative 

 estimation of cane sugar is of great value in analytical work. The 

 use of this enzym in studying the sugars which occur so widely dis- 

 tributed among plants is particularly recommended. 



THE PREPARATION OF INVERTASE. 



To prepare a stock solution of invertase, break up 5 pounds of 

 pressed yeast, which may be either baker's or brewer's yeast, add 30 

 cc of chloroform to it in a closed flask and allow it to stand at room 

 temperature (20 C.) over night. By the morning the solid mass will 

 have become fluid, and it should then be filtered through filter paper, 

 allowing several hours for draining. To the filtrate add neutral lead 

 acetate until no further precipitate forms and again filter. Precipi- 

 tate the excess of lead from the filtrate with potassium oxalate and 

 filter. To this filtrate add 25 cc of toluene and dialyze the mixture 

 in a pig's bladder for two or three days, using running tap water. 

 The dialyzed solution is colorless, perfectly clear after filtration, 

 neutral to litmus, has a solid content of about one-half of 1 per cent, 

 an ash content of a few hundredths of 1 per cent, will keep indefi- 



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