108 Chemical Manufactures. 



CHEMICAL MANUFACTURES, AS ILLUSTRATED IN 

 THE EXHIBITION OF 1862. 



BY J. W. m'GAULEY. 



It is probable that in no department of the Exhibition is the 

 progress of Science more clearly demonstrated than in that 

 which is devoted to chemical products. The various substances 

 which are found there, and the different compounds, are so 

 conveniently classified, and the specimens themselves are, 

 in many cases, such beautiful objects, that a careful inspec- 

 tion of them is attended with both profit and pleasure. What 

 can be more agreeable than the brilliantly white crystalline 

 masses of sal-ammoniac, alum, etc., or more pleasing to the eye 

 than the rich colours of the chromates and sulphates of copper, 

 prussiates of potash, and many other salts. And if perfect 

 crystallization, and either richness of colour or total free- 

 dom from it are to be considered as proofs of the purity and 

 excellence of the products, what are shown on the present occa- 

 sion must be admitted to be inferior to nothing that has ever 

 before been exhibited. The illustrations of chemical manufac- 

 tures presented to the student are particularly valuable, not 

 only because he can examine them without fatigue or trouble, 

 on account of their excellent arrangement, but because he will 

 see collected together a variety of substances with which he 

 could scarcely have been acquainted except by name. He will 

 find also, in several instances, the different phases of important 

 manufacturing processes placed before him, so that he can 

 trace their progress from their earliest stages to their comple- 

 tion. No branches of industry have derived more benefit from 

 science than those which depend on chemistry. Not only have 

 long-established operations been extended by it, and augmented 

 in usefulness through a greater economy of production, but 

 altogether new ones have been originated and developed. The 

 degree to which the cost of many useful matters has been 

 diminished is truly surprising : not to mention acids, and alka- 

 line salts, which, in our own time, were so much dearer than at 

 present, there are a number of compounds, the prices of which 

 bear no proportion to what they were at no distant period. 

 Thus Prussian blue was originally two guineas a pound ; it is 

 now less than two shillings. Ultramarine, when made from 

 lapis lazuli, was five guineas an ounce ; what is just as useful 

 may now be had for little more than a shilling a pound. 



We propose to treat, on the present occasion, of the manu- 

 facture of mordants and dyes : but the subject is so extensive 

 that we must confine ourselves to a comparatively limited view 



