CHEMICAL MANUFACTURES IN GLASGOW, ETC. 209 
while the bleaching' power still remained uninjured. They 
took out a patent for this discovery ; but it was infringed 
upon by the Lancashire bleachers; a law-suit was the conse- 
quence, and the patent was destroyed. It was then that Mr. 
Macintosh tried whether chlorine would not be absorbed by 
slacked lime. The trial succeeded ; a compound was formed 
which readily dissolved in water, and the solution of which, 
possessed great bleaching power ; a patent was taken out for 
the manufacture of this dry powder, which the patentees dis- 
tinguished by the name of bleaching powder. This patent 
was not infringed ; the sale of it was at first small, and it was 
overlooked by the bleachers. The consequence was, that the 
patentees had leisure to perfect their method of preparing it, 
and to become able to sell it at so low a price that it gradual- 
ly superseded all the old methods of bleaching by chlorine. 
The process may be seen at St. Rollox's in great perfection 
and on a very large scale. The requisite mixture of common 
salt, binoxide of manganese and sulphuric acid, is put into a 
leaden still, and the chlorine evolved -passes through leaden 
tubes into air tight stone chambers, the bottoms of which are 
covered with a stratum of slacked lime, several inches thick. 
The lime absorbs the gas as it passes into the chamber, and 
the process is continued, until the absorption is reckoned suf- 
ficient. 
Bleaching powder, supposing it pure, is a compound of 
1. Chloride of calcium, 7 
2. Chlorite of lime, 10 
3. Water, 3.375 
20.375 
Half the lime loses its oxygen, and combines with chlorine, 
constituting chloride of calcium. The oxygen combines with 
chlorine, which, in the state of chlorous acid, combines with 
the other half of the lime, constituting chlorite of lime. Two 
atoms of water were in the slacked lime. The third atom 
VoTi. vii.— No. nr. 27 
