Arsenic is occasionally used in the arts. It is employed in various metallic combinations where a white colour is required, and, particularly, for the whitening or bleaching of copper, which is thereby also rendered capable of taking a fine polish; hence its use in many of the compositions for the mirrors of reflecting telescopes, and for other optical instruments. The manufacturers 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 extent in Bohemia and Saxony, by roasting cobalt ores for the manufacture of zaffre (247). _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. It is employed as a poison for rats and mice; and, diluted with water, it attracts and poisons flies, whence it is sometimes called by the French, _poudre a mouches_. There cannot, however, be too great caution used either in the preparation, or in the application, of this fatal poison. 243. _YELLOW ORPIMENT is a mineral substance of lemon colour, which consists of arsenic in combination with sulphur; and in the proportion of about fifty─seven parts of the former and forty─three of the latter._ _It is about thrice as heavy as water; and is found both in a massive and crystallized state; but the crystals are so confused that their figures cannot easily be determined._