Dr. Playfair’s Lecture on the Great Exhibition of 1851. 25 
being collected and economized ; yet in spite of these well ascer- 
tained facts, there are scarcely half a dozen furnaces in the United 
Kingdom where this economy is realized by the utilization of the 
waste gases of the furnace 
Large quantities of ammonia are annually lost in iron smelting, 
which might readily be collected. Ammonia is constantly in- 
creasing in value, and each furnace produces and wastes at the 
least 1 cwt. of its principal salt daily, equivalent to a considerable 
money loss. With the low price of iron, this subsidiary product 
is worthy of attention. As I write, a Welsh smelter has visited 
me, to say that he has adopted this suggestion with advantageous 
results. I might adduce other improvements introduced by chem- 
istry in the smelting process; but these will suffice to show you 
that she has added to human power by increasing. production, 
while she has also economized both the time and the materials 
employed. - 
moisture. A great improvement was made in Scotland, by sub- 
stituting sulphuric acid for sour milk; and the immediate effect 
was, to reduce the time from eight to four months. In 1785, a 
French chemist suggested the use of chlorine as a means of 
hastening the process, and, in the last year of the eighteenth 
century, a compound of this gas with lime was introduc 
Tennant of Glasgow. The development of the cotton manu- 
acture now became immense. . By a happy adaptation of other 
chemical processes, in conjunction with the bleaching power of 
chlorine, the time required for the whitening of cotton and 
linen fabrics was at once reduced from months to hours, while 
the miles of outstretched calico, defacing the verdure of country 
districts, disappeared, the whole operation being carried on 
within the small space of an ordinary factory. You may ima- 
gine what an impulse this gave to a trade so important to us. 
The bleaching of calico now consists of a chemical operation of 
great precision; that of silk and wool has not yet been so thor- 
Srconp Serims, Vol. XIV, No. 40.—July, 1852. 4 
