THE DUBLIN INTERNATIONAL EXHIBITION. 223 
merce, and yet it bids fair to become one of the most important of the 
sodium products. The specimens shown by the above firm are examples 
of the perfection to which any individual article of industry may rise in 
a short time if there is a demand. Independently of the use of this pro- 
duct by the soap and other manufacturers, there can be no doubt that 
the late American war, from the restriction it put upon the potassium 
compounds, gave an impetus to the caustic soda trade. This soda is now 
largely exported to America and Australia Messrs. Hutchinson and Co. 
also show a specimen of precipitated sulphur, procured from the sulphide 
of calcium, of the alkali waste. If they can successfully carry this out, 
they have solved one of the most difficult problems of the alkali manu- 
facturers. The great weight of the material that has to be handled, 
combined with the nuisance arising from the working has been so far a 
prohibition to the adoption of many of the numerous processes intro- 
duced. 
In connection with this class of manufactures we may notice a fine 
case of platinum stills^syphons, and other apparatus, exhibited by 
Messrs. Johnson, Matthey, and Co., London (United Kingdom, 21). 
These articles are all soldered by fusing the seams together, instead of 
using gold — a more perfect joint is by this means procured, at a less 
expense. This case raised, some time since, a friendly discussion* 
between Messrs. Johnson and Co. and the reporter, in reference to the 
substitution of glass for platinum in the concentration of sulphuric acid. 
The real position, in the opinion of the reporter, as regards this impor- 
tant point is, that the advantages and disadvantages are so nearly 
, balanced, that in England, where fuel is not of so much importance, the 
manufacturers are reverting back to the glass ; but that on the Conti- 
nent, fuel being of greater consideration, the platinum still holds its 
ground, and is likely to do so, from its greater economy in this respect. 
This firm also shows some specimens of the refractory metals and 
rare metals, which could hardly have been produced in such quantities 
had it not been for the experiments of Deville, Debray, and others. 
Products of the Magnesium Company (Sonstadt's patent) are exhibited 
by this firm ; and as we owe the production of this metal, in a commer- 
cial aspect, entirely to the latter gentleman's perseverance, a special 
medal would have been awarded, but that the rules of the Exhibition 
Committee prohibit any but exhibitors from receiving medals. Messrs. 
Johnson and Sons, London (United Kingdom, 22), show a case, perhaps 
less pretentious, but containing products equally good. Gold, silver, 
and uranium salts, are also well shown in both these cases. 
In iodine and bromine products, Messrs. Tissier and Son (France, 7) 
show some fine specimens, the iodide of mercury being crystals got by 
sublimation instead of the ordinary process of precipitation. The French 
and German firms had almost entirely the supplying of the British 
* 'Chemical News,' June 16 and July 7, 1865, 
