1915] 



DAVIS ENZYME ACTION IN MARINE ALGAE 791 



third their volume, when the scum that formed was filtered 

 off; this filtrate was then further evaporated to about one- 

 fifth the original volume on the water bath. At this point 

 the two lead acetate portions were placed together. Ninety- 

 five per cent alcohol was added to each of the lots to about 

 80 per cent concentration when a flocculent precipitate came 

 down rather slowly. With the Ba(OH) 2 portion this was 

 copious, with the lead acetate, slight. After two hours the 

 precipitates were filtered off, washed with absolute alcohol, 

 redissolved in a small amount of distilled water, and then 

 reprecipitated with 4 volumes of absolute alcohol, the result- 

 ing precipitate being dried over CaCk. From the Ba(OH) 2 

 portion, 4.2 grams of a creamy white powder were obtained 

 that gave a very slightly reddish tinge with iodine, did not 

 reduce Fehling's, and was easily soluble in water, giving a 

 clear solution. Upon hydrolysis with weak H2SO4 a reducing 

 sugar was split off. The lead acetate portion gave but two 

 grams of the same material. This powder was taken to be the 

 laminarin described by Kylin. 



The determination of reducing sugars. — The reduction of 

 copper, or in the case of maltose and lactose, the increase in 

 the reducing value of the substrate plus the enzyme over that 

 of the checks, was taken as the measure of carbohydrate 

 hydrolysis. In this determination the permanganate titra- 

 tion method, as modified and described by Shaffer ('14), was 

 used, it being possible with it to determine amounts of sugars 

 as low as 2 milligrams 1 very accurately and quickly. Shaffer's 

 description may not be generally available to plant workers 

 who may desire to use this really splendid method, and so 

 the various steps in the process as used here are set down in 

 some detail. 



Ten cc. of the carbohydrate-enzyme substrate were placed 

 in a large test-tube containing 5 cc. of water, and just brought 

 to a boil. At this point a drop of 50 per cent acetic acid was 

 added. When the slight protein precipitate formed, 5 cc. of 



1 Shaffer determines values below two milligrams, but as used here, con- 

 sistent results could not be obtained where less than that amount was involved. 

 Below this point the relative increase in the experimental error is large. 



