CHEMISTRY. 828 



Comparison of volumetric methods of tannin analysis with, hide-powder 

 method, II. R. Procter and A. B. Searle (Mss. Tech. Beil. Ledermarkt, 2 [1901), p. 

 60; (lbs. in Cheiit. Ztg., 25 {190 1), No. SO, Reperl., j). 2S.3) .—By the Jean method the 

 results were lower than by the Lowenthal method and much lower than by the hide- 

 powder metho<l. There was no constant relation between the results oljtained by 

 the 8 methods. 



Studies of the pentosans of jute, vegetable sponge, and brewers' grains, 

 A. ScniixE and P.. Tom.ens {Jotti: hiiidir., .}9 {1901), X<j. 1, jip. S'i-;A?).— The 

 autliDrs made a study of the pentosans of the substances named, and the application 

 of various modifications in the methods of analysis. Comparisons were made l)etween 

 heating on the water bath in the usual manner and heating under pressure. Lower 

 results were obtained by heating in an autoclave at 125 to 118°, with 1 per cent sul- 

 phuric acid, than heating with 5 per cent sulphuric acid in the water bath. By 

 digesting jute with dilute soda solution and precipitating with alcohol 4.6 per cent of 

 wood gum was obtained, representing 1.2 per cent of xylose. The vegetable sponge 

 yielded 0.(53 i)er cent of xylose. Brewers' grains heated in the water bath with 3 

 jier cent sulphuric acid yielded 24.77 per cent of pento.sans, equivalent to 28.16 per 

 cent of pentoses. The treatment was found to have extracted the pentosans and 

 inverted them to pentoses quite completely, although the residue continued to show 

 the lignin reaction. 



The constituents of the tea leaf, and the changes which these substances 

 undergo during the manufacture of tea, A. W. N.\nninga {Meded. \S Lands, 

 I'l(i)ilt')iliiin, 1901, No. 46, pp. 60). — This contribution treats of the quantitative 

 determination of caffein, tannic acid, and some other soluble constituents of the tea 

 leaf. The methods of v. Romburgh and Lohniann of extracting with alcohol, and 

 that of Vite of extracting with water, were carefully tested with samples having a 

 known caffein content. It was found that the alcohol method could not be used for 

 green tea nor for freshh' dried leaves because giving too low figures, while for black 

 tea both methods gave practically the same results. Further tests showed that the 

 cause of the vm.satisfactory results obtained with the alcohol method were due to the 

 ])resence of the tannic acid, and that it was not practicable to satisfactorily extract 

 caffein with chloroform from an aqueous solution when tannic acid is present. The 

 water method failed to return quite all the caffein present in the green and in the 

 freshly dried leaf. The methorl finally adopted was that of extracting with chloro- 

 form. This method also was the most satisfactory in analyzing coffee and kola nuts. 

 The residts of the several methods with fresh, dried, an<l fermented tea leaves are 

 shown in tal)les. 



Great difference of o])inion has long existed regarding the properties of the tannic 

 acid of tea. This is probably due to impurities in the extract, and to avoid tliis the 

 author devised a method for obtaining pure tannic acid from the leaves. It was 

 found that the presence of 20 per cent water in the powdered tea made possible the 

 complete extraction of the acid, which was impo.ssible with dry leaves. The tannic 

 aci<l of tea is very hygroscopic and deliquesces at once, assuming a yellowish-brOwn 

 color and a sirup-like consistency. The characteristics of the dry ]>ow<ler as regards 

 solubility, taste, and reactions with a variety of chemicals are given. The iletlection 

 of the plane of polariz<'d light is ]tra<-tically constant for different sanq)les — about 

 3.4°, showing that the tannic acid of tea is a jture chemical combination and not a 

 mixture as tannin. 



The peculiar property fif l)eing absorbed by hide i>owder was tested with the tan- 

 nic acid of tea. The cont^lusion was rea(;hed that in the quantitative determination 

 of tannicr af^id it is necessary to add the hide powder in small amounts every 10 

 mimites. If the entire amount is ad<led at once there is at first a rapid absorption of 

 the acid, followed by a decrease in the absorptive power of the hide powder, so that 



