KNAPP'S CHEMICAL TECHNOLOGY. 281 
The work before us differs, in several respects, from other 
works on the subject in its arrangement. The author has 
placed his subjects in groups, two of which constitute the pre- 
sent volume. First, branches of manufacture depending 
upon the process of combustion, including, 1st, heat, fuel, the 
applications of heat, direct and indirect, in the construction 
of furnaces, draft chimneys, steam heat, &c ; 2d, of illumi- 
nation and lighting materials, including the manufacture of 
gas, the construction of lamps and the fuel that serves them. 
The first embraces the important processes for charcoal and 
coke ; the second, the mode of extracting various fatty sub- 
stances, used in illumination, as stearine, stearic acid, wax, 
the fixed oils, &c., &c. The chapters on gas manufacture 
are particularly well illustrated with cuts, exhibiting the 
various steps of the process. The old adage of " a penny 
saved is two pence gained," applies in large manufactures, 
as in the daily routine of domestic life, and whilst we repu- 
diate niggardliness equally in either case, we rejoice at the 
application of a wise economy in both. 
The second group, consisting of processes concerned in 
the production and application of the alkalies and earths, is 
much more extensive than would be at first imagined, as it 
embraces a number of collateral and resulting branches, 
and is that part most interesting to the pharmaceutist. The 
important bearing that sulphuric acid has in so many pro- 
cesses, has caused it to be treated of in this connection in 
the extraction of sulphur from its natural sources ; the pro- 
duction of sulphuric acid, with the modus operandi of the 
lead chambers ; the concentration of the acid, &c. We ap- 
pend a specimen of the illustrations exhibiting the expensive 
platinum arrangement for concentrating the acid from sp. 
gr. 1.7 to 1.84, together with the refrigerating syphon. 
26 
