374 EXPERIMENT STATION RECORD. 



starch credits them with from 4 to 00 ]>cr (-(mt of tho sairic. Even 15 luimites' warra- 

 ing with very dilute hydrochloric .acid gives an ap]treciable aiuouut of what we are- 

 bound to interpret as starch. This brings lis to the inevitable conclusion that other 

 bodies than starch are present and respond toward each of these reactions in the 

 same way as starch does. We know, moreover, that the pentosans are such bodies, 

 and that they are invariably present to a greater or less degree in materials of th© 

 kind under examination." 



Portions of i)eiitos;iii (xylaii) isolated from wheat stra\v were treated 

 according to the first, second, third, and fifth methods for starch meu- 

 tioued above. 



"These results sliow conclusively that the pentosan, which is most characteristic 

 of feeding stuffs, and which has been shown to occur m all such materials, behaves 

 toward the reagents named in precisely the same manner as starch, ami in a no less 

 marked degree. Tlie conclusion is unavoidable that none of the methods for deter- 

 mining starch, based upon the above principles, can be employed with any degree 

 of accuracy u])on grains or forage plants or any materials where the i)resence of 

 these pentosans is probable." 



The most hopeful means of avoiding this diflftcitlty tlie author believes 

 to be removing the starch from the accompanying carbohydrates by 

 some solvent that does not affect the latter, and suggests diastase for 

 this purpose. This is a familiar method of starch determination which 

 has been shown to yield accurate results with pure starch. Although 

 the effect of diastase on the pentosans has not been thoroughly stud- 

 ied, some preliminary tests by the author indicate that these bodies 

 are not affected by diastase. 



Determination of starch by alcoholic fermentation, A. Munsche 

 ( Wochenschr, Brmierei, 9 {1894), p. 795; abs.- in Chem. Ztg., 18 {1894), 

 No. 70, Repert., p. 215). — The author dissolved pure starch by means of a 

 cold-prepared malt extract and then allowed the mash to ferment with 

 yeast species, causing superficial fermentation. The starch was de- 

 termined either from the carbon dioxid or the alcohol resulting. The 

 experiments showed that starch could be completely inverted with 

 diastase by barley malt and that with an absolutely pure fermentation 

 by means of yeast (''class -5"), the fermentable inversion products 

 could be fermented to the last trace in 00 hours. On an average 

 100 gm. of dry, i)ure yeast gave 51.20 gm. of carbon dioxid and 53.4:3 

 gm. of alcohol. Tlie author considers it feasible to quantitatively 

 determine the starch content by means of diastase and fermentation, 

 as described above, and states that the method is free from the error 

 arising in the ordinary method from other nitrogen-free extract, since 

 the gums are not fermentable. 



Investigations concerning the glycerol content of wine, P. 

 KULISCH {Forsch. ii. LebensmtL, 1, 2>P-2S0-28d, 311-318, 301-373).— T\\q 

 author considers the glycerol method of Neubauer and Borgmaim 

 inaccurate and unsatisfactory. The glycerol obtained by that method 

 is far from pure, as it contains albuminoids and other substances insoh 

 uble in water, and sometimes an appreciable amount of sugar. Accord- 

 ing to him the limits for the glycerol alcohol ratio suggested by those 



