viii TESTS FOR ENZYMES 165 



(12) Filter, and wash the residue on the paper with 

 absolute alcohol as before. 



(13) Eemove the alcohol by means of pressure and 

 by drying at 40 C. 



(14) Complete the drying in vacua over sulphuric acid. 

 The resulting powder is invertine. 



Instead of using dried yeast, a suspension of yeast in 

 lukewarm water may be shaken up with an equal volume 

 of chloroform in a shaking machine for twenty to thirty 

 minutes. 



The chloroform should be allowed to settle, and the 

 supernatant watery suspension poured into three times its 

 volume of 90 per cent spirit. 



The resulting precipitate must be treated as described 

 above under (8) to (14). 



Tests 



(1) Add a little of the powder to two test-tubes con- 

 taining a dilute solution of cane sugar, and keep the tubes 

 at 38-5 C. 



Test one tube with Fehling's solution after four to 

 six hours : reduction of copper, no alcohol. 



Test the other tube with Fehling's solution after 

 twenty-four hours : reduction of copper, no alcohol. 



(2) Heat some of the dry powder to 100 C. for a few 

 minutes, and then add a little of it to two test-tubes 

 containing a dilute solution of cane sugar. Keep the tubes 

 at 38-5. 



