1867.] Chemistry. 395 



Gun cotton is however hygroscopic, and on this account has been 

 found uncertain when made into cartridges. A sportsman, for ex- 

 ample, would make good shooting in the early part of a damp day, 

 bad in the middle, and worse in the afternoon. This objection to 

 the use of gun cotton, so much to be recommended on other 

 accounts for sporting purposes, has been obviated by the Messrs. 

 Prentice, who now enclose each charge in the thinnest possible 

 coating of india-rubber, by which the access of moisture is com- 

 pletely prevented. 



Of two other important papers communicated to the Koyal 

 Society we can only give the titles. The first is by Mr. H. C. 

 Sorby, " On a Definite Method of Qualitative Analysis of Animal 

 and Vegetable Colouring Matters by means of the Spectrum Micro- 

 scope."* This is really a continuation of the experiments described 

 in an article in our own pages, f made with improved apparatus 

 and a more definite aim. The paper requires very careful reading 

 at length for the full understanding of its contents. While on this 

 subject we may refer the reader interested in the matter to a 

 valuable paper by M. Preyer, " On the Quantitative Determination 

 of Colouring Matters of the Blood by means of the Spectroscope.":]: 



The next is a paper by Sir B. Brodie, read May 3rd, and entitled 

 "The Calculus of Chemical Operations: being a Method for the 

 Investigation, by means of Symbols, of the Laws of the Distribution 

 of "Weight in Chemical Change." For this, which will be a sealed 

 book to all but chemists familiar with the higher branches of 

 algebra, we must refer the reader to the original paper in the 

 ' Philosophical Transactions,' or a useful abstract in the ' Chemical 

 News ' for May 31st. 



A few processes of technical interest have been brought to notice 

 within the past quarter. Among these is one by Stolba, for easily 

 obtaining Sulphurous Acid on a large scale. When sulphate of iron 

 or sulphate of copper is heated with sulphur, sulphurous acid is 

 given off, and the sulphate is reduced to sulphide : — 



FeO, S0 3 + 2S = FeS + 2 SO,. 



To carry out this process practically, two-and-a-half parts of dry 

 sulphate of iron are mixed with one part of sulphur, and heated in 

 an iron retort, provided with a tolerably wide exit tube. This 

 process perhaps may be made available in some manufactures. 



A great advance has been made in the manufacture of aniline 

 dyes by MM. Girard and De Laire, who have succeeded in ex- 

 tracting three new dyes from the residues of the manufacture of 

 rosaniline, in which one half the aniline employed has hitherto been 



* ' Proceedings of Eoya] Society,' vol. xv., p. 433. 



t Vol. ii., p. 98. 



X ' Annalen der Chemie u. Pharm.' Bd. 140, p. 187. 



2 d 2 



