THE PREPARATION AND DIALYSIS OF THE INVERTASE SOLU- 



TIONS. 



The irivertase solutions were prepared from yeast by the rapid 

 process, previously described,* 1 modified in certain particulars so that 

 it now reads as follows : Crumble pure compressed yeast by hand and 

 knead it with an equal weight of water at ordinary temperature, 

 saturate the liquid with chloroform and keep it at 20 to 30 C. for 

 forty-eight hours. Add neutral lead acetate to slight excess, filter 

 the solution, remove the excess of lead from the filtrate with potas- 

 sium oxalate and repeat the filtration. Then saturate this filtrate 

 with toluene and preserve in an ice box. 



In order to free the solution of invertase from salts and other 

 impurities a thorough dialysis was performed. The solution was 

 held in a cone of parchment paper which rested in a large funnel on 

 porcelain rings affording a free passage for running tap water 

 between the paper and the funnel. The marked changes which took 

 place in the composition of the solution during dialysis are shown in 

 Table 1; they consist in a removal of large quantities of the total 

 solids, including nearly all the nitrogenous and ash bearing sub- 

 stances. The strong yellow color of the solution also disappears 

 almost completely during dialysis. 



TABLE 1. Change* i 



yeast juice (luring dialysis. 



A record of the enzymotic activity of the solutions is shown in 

 the second and third columns. The natural activity is that of the 

 solution without the addition of any acid to activate the invertase; 

 this activity does not show the amount of invertase that is present 

 in the solution because the activity depends greatly on the slight 

 traces of acid or alkali that are present. The maximum activity is 

 that of the solution after a few drops of acetic acid are added to bring 

 the acidity to a point at which it is practically independent of slight 

 changes in acidity; this maximum activity is a correct indication of 



a U. S. Dept. Agr., Bureau of Chemistry Cir. No. 50, p. 1. 

 [Cir. 55] 



