ARSENIC. 213 
capable of taking a fine polish ; hence its use in many 
of the compositions for the mirrors of reflecting tele- 
scopes, and for other optical instruments. The manu- 
facturers of glass frequently employ the oxides of 
arsenic in the fabrication of that article. Arsenic is 
used in the processes of dyeing and calico printing; 
and for the imparting of different artificial shades and 
colours to furs. It is also used in the manufacture of 
small shot, from its rendering the lead more brittle, and 
better capable of being formed into grains, than it 
would be without such admixture. 
The arsenic of commerce is prepared to a great ex- 
tent in Bohemia and Saxony, by roasting cobalt ores 
for the manufacture of zaffre (^47). White arsenic is 
made, by mixing the common oxide with potash, and 
submitting it to a certain degree of heat, in vessels 
adapted to the purpose; the arsenic, rising in fumes, is 
separated, leaving the sulphur behind, united to the 
potash. This process is called sublimation. 
Of all substances with which we are acquainted this 
is perhaps the most deadly. If only a few grains of it 
be taken into the stomach, it proves fatal; and it has 
frequently proved the more injurious from its deceitful 
appearance, in which it somewhat resembles salt or 
white sugar. Carelessly left in places open to the 
access of children, arsenic has not unfrequently been 
mistaken by them for sugar, and has been attended 
with the most dreadful consequences. If thrown on 
heated coals, however, it is immediately known, by 
the smell of garlic, and the white fumes which it 
gives out. The best remedy for this poison is said to 
be a few scruples of liver of sulphur (sulphuret of 
potash), dissolved in half a pint or a pint of water, and 
administered a little at a time, as the patient can 
bear it. 
Notwithstanding its deleterious qualities, arsenic is 
occasionally used in medicine, though in extremely 
small doses ; and it has, in particular, been found 
efficacious in many cases of intermittent fever. 
