CH. xm.] 



DIASTASE. 



359 



drop by drop, to obtain a complete separation of the protein (care 

 must be taken to avoid an excess) . Raise the temperature to boiling 

 and keep it so for a few minutes. Filter the urine through a small 

 paper that has previously been washed, dried and weighed. Wash 

 the precipitate in turn with hot water, 95 per cent, alcohol and ether. 

 Dry the paper and precipitate in an air bath at 110 C. till the weight 

 is constant. The weight of protein in 50 cc. is obtained by subtract- 

 ing the weight of the paper. 



M. Diastase. 

 422. Wohlgemuth's method. 



Principle. Varying amounts of urine are added to a given amount of 

 soluble starch, and the mixture digested for 30 minutes at 38 C. After cool- 

 ing, a drop of dilute iodine is added to each tube. The tubes that contain 

 considerable amounts of urine have all the starch digested so that no colour 



1 s obtained on adding the iodine. The tube with the smallest amount of urine 

 that completely digests the starch is found and so the diastatic value calcu- 

 lated (see p. 192). 



Reagents required. 



1. Stock solution of soluble starch. Accurately weigh out 2 grams, of 

 soluble starch (see p. 391) and transfer it to a dry test-tube. Add about 

 10 cc. of distilled water and shake. Pour the suspension into about 70 cc. of 

 boiling distilled water and stir well. Wash the tube three successive times with 

 5 cc. of distilled water, transferring the washings to the boiling solution. Now 

 add 10 grams, of pure sodium chloride. Allow to cool and make the volume 

 up to 100 cc. with distilled water. The solution is stable for months. 



2. One per mille soluble starch in 0-5 per cent, sodium chloride. 5 cc. 

 of the stock are diluted with distilled water to make 100 cc. This solution 

 must be freshly prepared each day. 



3. N/50 iodine, prepared from N/io iodine (see p. 390) by diluting 



2 cc. with 8 cc. of distilled water. The diluted iodine must be freshly prepared 

 each day. 



Method. Label a series of clean dry test-tubes i to 10. 

 Into the tubes measure the volume of urine and of distilled 

 water stated in the table, using guarded pipettes (see Note 7). 



