CH. XVl] DIASTASE. 305 



the time required for transforming a given weight of starch 

 are not reliable, since there does not appear to be a simple 

 relation between the rate of change and amount of diastase 

 causing it. 



Or 



The volumes of extracts required to completely change 

 a given weight of the substance in a given time may be 

 found by trial. The activity of the extracts will be 

 roughly proportional to the volumes used. 



[A discussion of processes for comparing the diastatic 

 activity of tissues is given by Brown and Morris, loc. cit. 

 p. 637 ; the same principles will apply to other ferments.] 



Preparation of a Ferment. (Diastase.) 



Make an aqueous extract of malt, using about 100 c.c. 

 of water for each 10 grs. of malt taken. 



Mash up the solid as completely as possible in a mortar 

 Avith a little warm water, transfer to a bottle, adding more 

 water, and shake for two hours. Then heat for half-an- 

 hour at 50° — 55° C, filter and concentrate the aqueous 

 solution under reduced pressure to a small bulk. 



To the concentrated aqueous solution add 90 p. c. 

 alcohol so long as it causes a flocculent precipitate, ceasing 

 the addition of alcohol when it begins to render the liquid 

 distinctly turbid or markedly opalescent ; filter off the 

 precipitate, wash it with absolute alcohol and dry in an 

 exhausted desiccator over sulphuric acid. 



The solid is impure diastase. 



Experiments on Diastatic Ferments. 



(1) Prepare a specimen of diastase. 



D. A. 20 



