222 MANGANESE. 
of drying ink after writing. The same substance re- 
duced to a perfectly fine or impalpable powder, is the 
article which is sold under the name of powder -blue, 
and which is not only used by laundresses and others 
in the getting up of linen, but also as the basis of 
several kinds of paint ; and by the manufacturers of 
writing and printing papers, to give a blue tinge to 
those articles. 
A solution of the oxide of cobalt in spirit of salt 
(muriatic acid, 29) and afterwards diluted till nearly 
the whole of its colour disappears, forms one of the 
most beautiful sympathetic inks with which we are ac- 
quainted. If a landscape be drawn with Indian ink, 
and, afterwards, the foliage be washed over with this 
solution, it will have no peculiar appearance; but, on 
holding the paper near the fire, the part representing 
the vegetation will gradually assume a green tint, 
which will subside on removing the paper into a cool 
situation. 
248. MANGANESE, in tie state that we usually see it, 
is a black oxide of a metal which is (rf a silvery grey colour, 
of leafy or foliated texture 9 and somewhat more than six times 
as heavy as zoater. 
Mines of manganese have long been worked in se- 
veral parts of Great Britain, but particularly in the 
counties of Devon and Somerset. Near Exeter and 
in the Mendip Hills this mineral is found in great abun- 
dance. 
It is employed for various useful purposes. In the 
manufacture of the finer kinds of glass it is used in a 
double capacity, both as a colouring material and as a 
destroyer of colour. As a colouring ingredient, the 
imitators of several precious stones are indebted to it 
for the red and purple tints which they give to the 
oriental ruby, the balais ruby, and the amethyst. 
The violet colour given to porcelain is obtained from 
manganese. This substance is also used for the glazing 
of black earthen ware, as a paint, and an ingredient in 
