286 
KWAPP'S CHEMICAL TECHNOLOGY. 
diately followed by a detailed account of the soda manu- 
facture, in which salt and sulphuric acid are so largely 
employed. This intiportant process is so luminously explained 
by descriptions and cuts, that the general reader, though 
but little versed in chemical matters, can get a clear idea; 
and the fact that the English revisers have brought it up 
to the present state of the art in that country, will ensure 
its authority to the manufacturer. It remains to be seen 
what effect Mr. Tilghman's Patent will exert on the process 
at present in use. The dependence of one branch of manu- 
facture on another is beautifully illustrated in the connec- 
tion of the production of sulphuric acid, carbonate of soda, 
muriatic acid, chloride of lime and bi-carb. soda ; indeed, 
it is only by the consumption of the residues that these 
articles can be manufactured at such low rates. The 
production of potashes from all the commercial sources 
is fully dilated on, and their relative value to the manu- 
facturer exposed. Boracic acid and borax next occurs, 
followed by the fullest history of the saltpetre production 
that we have met with in a work of this kind. The natu- 
ral sources of this substance, from caves, as in our own 
country, and earthy deposits in the East, are exposed ; and 
the several modes of conducting its artificial fabrication in 
what are termed the saltpetre plantationsof Europe, which, 
though artificial, so far as the bringing together the mate- 
rials is concerned, is probably the identical natural process 
that ever occurs when nitrogenous and alkaline and earthy 
matters mixed in a moist state, are exposed to the atmos- 
phere for a long time, and which is known by the term 
nitrification. The chemical changes which result in the 
generation of nitric acid, appear to be, first, the conversion 
of nitrogen into ammonia, and the subsequent oxidation 
of this into nitric acid and water, by a sort of fermentative, 
(catalytic) action, which, though much has been done by 
