PROGRESS OP CHEMISTRY IN SOUTH LANCASHIRE. 109 



been verbally communicated to them by various gentlemen practically engaged 

 in the chemical manufactures of this neighbourhood, who have, in a most 

 liberal manner, not only opened their works to minute inspection, but have 

 themselves devoted a considerable amount of time and personal labour in 

 minutely explaining all those processes which they deemed of scientific in- 

 terest, thus throwing open their accumulated store of practical as well as 

 theoretical experience. 



Where the attention and interest shown by all the numerous gentlemen to 

 whom the authors had occasion to apply has been so great, it appears almost 

 invidious to mention any names; but in thanking all, the authors cannot for- 

 bear to state that to Messrs. Roberts, Dale and Co. of Cornbrook, Mr. Gos- 

 sage and Mr. Deacon of Widnes, Mr. Spence of Pendleton, Mr. Shanks of 

 St. Helens, and Mr. Higgin and Mr. Hart of Manchester they are especially 

 indebted for a large amount of valuable information. 



In conclusion, it may be stated that it has been the aim throughout the 

 Report to describe the various improvements effected during the last ten years 

 so far only as they are of scientific interest, and carefully to avoid entering 

 into those details of manufacture whicli to a great extent regulate the economic 

 production of the article, and which, though they are all-important to the 

 trader, are of slight interest to the man of science. 



I. Sulphuric Acid. 



No substance produced by the manufacturing chemist is equal in import- 

 ance to sulphuric acid, since it is quite indispensable in the production of 

 many other articles, as well as in many manufacturing processes. In the 

 production of soda-ash, and consequently of soap and glass, of muriatic, 

 nitric, and other acids, of alum, sulphate of copper, bleaching powder, &e., 

 in bleaching and dyeing, its use is quite essential. To produce it econo- 

 mically on the large scale is therefore an object of considerable importance, 

 and numerous improvements have consequently been introduced into the 

 manufacture with the view of bringing it to the highest state of perfection. 

 In order to give an idea of the degree of economy practised, we may men- 

 tion that an eminent manufacturer informs us tiiat he obtains from 100 parts 

 of sulphur 280-290 parts of sulphuric acid of sp. gr. 1-85, which, even sup- 

 posing the sulphur to be pure, is as near the calculated quantity (306) as can 

 be expected in practice. Very few manufacturers, however, employ sulphur ; 

 most of them use pyrites, the only objection to the latter being that it con- 

 tains arsenic, so that the product is consequently contaminated with arsenious 

 acid. The Irish pyrites contains 33 per cent, of sulphur, whilst the Spanish 

 pyrites contains as much as 46 per cent. The ordinary burner for pyrites is 

 well known, and answers sufficiently well when the ore is in large lumps, 

 since the quantity of sulphur left in the residue does not exceed 3 per cent. ; 

 but considerable difficulty is experienced in operating on the smaller pieces 

 and powder, technically called smalls. In burning these in the ordinary 

 way, in the case of Spanish pyrites, from 8 to 10 per cent, of sulphur remains 

 behind and is lost. By mixing them with clay and forming the mixture into 

 balls before burning, this loss may be reduced to about 4 per cent. It is 

 indeed possible to continue the operation until the quantity of sulphur left 

 unconsumed amounts to only 2 per cent., but the time required for this pur- 

 pose is found to be too long to make it worth while to do so. Mr. Spence 

 of Manchester has, however, devised a plan for effecting this object in an 

 economical manner, which may be shortly described as follows : — In the first 

 place the smalls are riddled out, the large lumps being put into the ordinary 



