W. A. Davis and G. C. Sawyer 363 



"Soluble StarcJr' {or dextrin) in Aqueous Extract. 



150 cc. of the 250 cc. were left with 0-1 grm. of taka-diastase and 

 1 cc. of tohiene for 24 hours at 38° ; to the sohition 5 cc. of basic lead 

 acetate solution were then added, which was just sufficient to precipitate 

 the whole of the tannins, gums, etc. The solution was diluted to 200 cc. 

 at 15° and filtered; the slight excess of lead in the filtrate was exactly 

 precipitated by adding solid sodium carbonate and the reducing and 

 rotatory powers of the filtrate determined. 



.50 cc. of the 200 cc. gave 0-0718 grm. CuO. 

 Rotation in 400 mm. tube at 20° = + 0-202°. 



Correcting for 0-1 grm. taka-diastase, under exactly similar conditions 

 (correction for CuO = 0-0360 grm. ; for polarisation = + 0-106°), we 



have 



CuO due to sugars present = + 0-0358 grm. 

 Polarisation due to sugars present = + 0-096°. 



It is necessary to correct for the reducing power and polarisation of 

 the original solution ; for the reducing power we have 



1 50 



^-^v! > 0-0217 = 0-0163 grm. 



As to the rotatory power, measurements made with the various 

 pickings in which "soluble starch" was entirely absent showed that if 

 the reducing substances be assumed to be sugars, with a cupric reducing 

 power 2-5 grms. CuO per grm., they had the specific rotatory power 

 [a]^ = + 25°. The assumption that this is the case when the soluble 

 starch is present will give no sensible error ; we have therefore a^, due to 

 these substances in a 400 mm. tube 



0-0163 25 X 400 x 2 _ , . .,oo 



We have therefore as final values for maltose and dextrose formed 

 by the diastase conversion : 



CuO ex 50 cc. = 0-0358 - 0-0163 = 0-0195 grm. 

 Polarisation in 400 mm. tube = 0-096 - 0-013 = 0-083°. 



If a: = dextrose in 50 cc. ; y = maltose in 50 cc, 



2-58a;+ l-38;y = 0-0195 



4-22a;+ 11-01«/ = 0-0830 

 Solving, X = 0-00443 grm. ; y = 0-00586 grm. 



