418 PRACTICAL ORGANIC AND BIO-CHEMISTRY 



5 c.c. of I per cent, starch solution are warmed to 40 and 1-5 c.c. 

 of diastase solution are added. The time is noted at which the mix- 

 ture is made. At intervals of -J to I minute a drop is removed and 

 tested against a drop of iodine solution. The time is taken at which 

 no colour is given, i.e. when the achromic point is reached 



Vernon 1 states that this method is very exact if corrected by 

 means of a table which he gives. 



(d) Wohlgemuttis Method. 



This method is carried out in a similar way to Lintner's method with 

 varying quantities of enzyme solution, but the disappearance of starch as 

 shown by the iodine reaction is taken account of. 



5 c.c. of i per cent, starch solution are placed in each of a series of 10 

 tubes and cooled to o, whilst an increasing quantity of enzyme solution is 

 added to each tube in the series. They are transferred to a bath at 40 for 

 30 or 60 minutes and after this time again cooled to o to stop the action. 

 Each tube is filled with water and one drop of *iN iodine solution is added 

 to each. The colours are blue, blue-violet, reddish and yellow. The limit 

 is taken as that tube which still shows a violet colour. The activity of the 

 solution is then calculated on the basis of the power of i c.c. enzyme solution. 

 Thus if the tube in the series contain 0-3 c.c. enzyme solution, then the 



diastatic power at 40 in 30 minutes or D 7 is -- = 16*6. 



It has been shown by Evans 2 that this method only gives certain values 

 for D, that the values are only approximate and that it is not accurate when 

 the volumes of saliva added are in geometrical progression. He finds that 

 the achromic point method is more delicate. 



(e) Other Methods. 



The reducing sugar may be estimated gravimetrically or by any other 

 method for estimating carbohydrates. Proteins, etc., should be removed before 

 the estimation (see under lactase). 



Pancreatic Diastase. 



The diastase of the pancreas does not hydrolyse properly except in the 

 presence of salts; -3 gm. of sodium chloride and 7 c.c. of -2N disodium 

 phosphate should be added per 100 c.c. of reaction mixture. 3 



1 J. Physiol., 27, 182. z lbid., 44, 220. 



'Sherman, Kendall and Clark, J. Amer. Chem. Soc., 1910,32, 1073. 



