1910.] 



Studies on Enzyme Action. 



353 



A second experiment, carried out with the same (juantities of gliicoside and enzyme 

 under similar conditions, gave the follosving results : — 



Time of 



Volume (c.c.) of 



Weight (gramme) of 

 prussic acid. 



Percentage of 

 hydrolysis. 



iictiou 

















Silver 

 solution. 



lodiuc solution. 



From 

 silver. 



From 

 iodine. 



From 

 silver. 



From 

 iodine. 



Hours. 















1 



3-7 



37 -3 



0 -01005 



0 -01021 



18-0 



18 -9 



2 



6-25 



(a) (4) 

 61 -5 GO 0 



0 -01698 



(a) 

 0 -01683 



31 -4 



(«) 

 31 -1 



3 



8-25 



81 -0 80 -5 



0 -02241 



0 -02217 



41 -5 



41 -0 



4 



9-8 



95 -5 94 -5 



0 -02663 



0 -02614 



49 -3 



48 -4 



5 



11 -1 



107 -5 105 -5 



0 -03016 



0 -02942 



55 -8 



54 -4 



6 



12 -2 



118 -5 116 -0 



0 -03315 



0 -03243 



61 -3 



60 -0 



7 



13 0 



129 -25 127 -5 



0 -03532 



0 -03537 



65 -5 



65 -5 



24 



17-45 



174 -4 



0 -04741 



0 -04773 



87 -7 



88 -3 



The titrations giving the values marked («) in the third column were effected in the 

 absence of starch, those marked {b) in its presence. It appears that this indicator fives 

 erroneous results when used under conditions such as were observed by us. We noticed, 

 in fact, that the coloration produced was very evanescent and that, unless the first 

 appearance of a colour which didinot vanish immediately on sliaking were taken as indi- 

 cating the end of the change, no definite result could be obtained. In all the experiments 

 except the first in the first table and the first and last in the second, an aliquot part 

 of the sample was titrated with iodine. As the experiments in wliich the whole of the 

 solution was titrated are also those in which the results afforded by the iodine method are 

 higher than the results on using silver nitrate, it would appear that there is some connexion 

 between the two facts. We do not, however, understand why this should be the case. 



We are led by our experiments to conclude that in estimating small amounts of 

 hydrogen cyanide such as were dealt with by Dunstan, Henry and Auld their method is 

 preferable ; but that in estimating the much larger amounts dealt with by us, the silver 

 method may be used with equal advantage. The iodine method has the disadvantage 

 that the titrations to be of any use must be effected immediately the sample is taken ; 

 this necessity restricts the use of the method to the daytime, unless starch be used as an 

 indicator : as we have stated, this has given erroneous results in our hands. 



Action of the " Enzyme" from Almonds on the Phaseolus Qlucosidc. — Ouv 

 experiments showthat the glucoside is invca-iablyhydrolyscd by almoud-emulsin, 

 although to a very minor extent ; the conflicting results of different workers 

 must be attributed to the use of enzymes of varying degrees of activity. In 

 our experience, commercial emulsin is a material of variable activity ; it is 

 usually weaker than the extract prepared in the manner described in our 

 previous communication. 



Equivalent M/5 solutions of the Phaseolus glucoside and of amygdalin, 

 containing per 100 c.c. 20 c.c. of a solution of almond-emulsin (Xo. XII, 

 p. 324) were hydrolysed, the one to the extent of 2-25 per cent., the other 'to 



