148 



CHEMISTRY. 



tions especially suited for their separation and 

 plastic reunion in the body." 



Prof. Clowes, examining some of the sand- 

 stones of the New Red beds near Nottingham, 

 discovered the presence of barium sulphate in 

 varying proportions, while some of the lower 

 beds also contained calcium carbonate. In 

 some of the beds the barium sulphate was 

 very unequally distributed, and formed a net- 

 work or a series of small masses more or less 

 spherical in shape. In such sandstone the 

 sand-grains between the sulphate streaks and 

 patches were quite loose, and the surfaces that 

 were weathered presented a honeycombed ap- 

 pearance. To explain the presence of the ba- 

 rium sulphate, Prof. Clowes suggests that it 

 might have been deposited along with the 

 sand ; but if such had been the case it had cer- 

 tainly undergone a physical change, as it now 

 existed in a firm, compact, and crystalline con- 

 dition. It would, therefore, appear that it 

 had been either deposited from aqueous solu- 

 tion or that it had been rendered crystalline 

 by a slow percolation of the solvent liquid 

 through the sedimentary deposit, or owed its 

 origin to the action of water containing calci- 

 um sulphate passing through sandstone cement- 

 ed originally with barium carbonate. 



The views concerning the transformation of 

 starch into sugar by boiling with sulphuric 

 acid, or the action of diastase, have been so 

 contradictory that the nature of the changes 

 which starch undergoes has remained open to 

 question. Musculus was of the opinion that 

 starch was split up into two molecules of dex- 

 trin and one molecule of sugar, and that later 

 the acid acted on the dextrin thus formed, 

 though very slowly. Payen asserted that 

 starch did not split up in the manner thus sup- 

 posed, under the influence either of diastase 

 or of sulphuric acid, but that a gradual trans- 

 formation took place. F. Salomon, who, by 

 the adoption of improved methods has suc- 

 ceeded in placing the reaction on a satisfactory 

 basis, first studied its beginning and end prod- 

 ucts starch and glucose and then the inter- 

 mediate products "soluble starch" dextrin, 

 and maltose particularly with regard to the 

 analytical processes involved in their determi- 

 nation. Allihn has shown that starch is never 

 entirely converted into sugar by the ordinary 

 process of action with dilute sulphuric acid 

 and the reducing solution of copper, 95 per 

 cent, being the maximum that can be obtained 

 by it. But if hydrochloric acid is used ac- 

 cording to the method of Sachsse, a complete 

 conversion may be effected. When pure sugar 

 solutions are used, the hydrochloric or Allihn 

 process is exact ; but if the solutions contain 

 other substances, good results can be obtained 

 only when special care is taken. Salomon 

 studied the action of dilute sulphuric acid in 

 an apparatus in which a certain amount of 

 starch solution could be boiled at a fixed con- 

 centration, and from which portions could be 

 easily taken for analysis at regular intervals. 



These portions were examined as to their ac- 

 tion on iodine solution, their rotatory power 

 and specific gravity. By the study of sixteen 

 observations, in some of which the boiling pro- 

 cesses were continued for twenty-eight hours, 

 it was seen that the change from one color to 

 another is very gradual ; that it always takes 

 place in the same order, viz., from deep-blue 

 to violet, red-violet, red, red-brown, brown- 

 yellow, yellow, and finally colorless ; and that 

 neither the complete extinction of the color 

 nor the individual shades correspond exactly 

 with the amount of sugar, formed as shown by 

 the rotatory power. 



Prof. H. Carrington Bolton has obtained 

 some very interesting results regarding the 

 action of citric acid, which is hardly less pow- 

 erful than that of hydrochloric acid on min- 

 erals. His later researches bear particularly 

 on the effects of prolonged action at ordinary 

 temperature. Of the sulphides, chalcocite 

 showed signs of decomposition at the end of 

 ten days, and gave, after several months, a 

 partial solution of a green color. Pyrite was 

 slightly attacked in eight days, and a month 

 later gave a reddish-yellow solution. Chalco- 

 pyrite acted in a similar manner, and lost 11 

 per cent, after fourteen months. Of the ox- 

 ides, magnetite and limonite were strongly at- 

 tacked in eight days, while haematite yielded 

 more slowly, but showed decided decomposi- 

 tion after several months. Of the silicates, 

 datolite was most quickly decomposed, yield- 

 ing gelatinous silica after twenty-four hours. 

 Hornblende, pyroxene, almandite, epidote, ve- 

 suvianite, and serpentine were decidedly de- 

 composed in eight days, while after fourteen 

 months hornblende and pyroxene were com- 

 pletely decomposed, and serpentine yielded a 

 dry, gelatinous mass. The feldspars were un- 

 equally attacked under like condition. Tour- 

 maline and staurolite yielded after four or five 

 months, while talc and cyanite seemed to' re- 

 sist attacks. Muscovite and biotite yielded 

 very slowly. Prof. Bolton has prepared a 

 table showing, after these results, the relative 

 disintegration of minerals by citric acid in solu- 

 tion, in which the minerals are classified as 

 those quickly decomposed, those slowly de- 

 composed, those very slowly decomposed, and 

 those not decomposed. To the last class be- 

 long quartz, corundum, spinel, beryl, fluorite, 

 and barite. 



J. R. Duggan has made experiments for the 

 determination of diastatic action. The princi- 

 pal conditions affecting the converting power 

 of substances containing diastase are time, 

 temperature, and the presence of various for- 

 eign substances, such as acids, alkalies, etc. 

 Previous experiments have shown that the 

 action of the ferment is very much retarded 

 by the presence of quite small amounts of 

 alkali. "When greater quantities of alkali are 

 used, there is little or no conversion. The 

 author's experiments on the influence of acids 

 have led him to doubt the general statement 



