পাতা:পদার্থবিদ্যাসার.djvu/১৮৩

17.2 Tut. In addition to this, when applied in small quantities, it aids digestion. In larger quantities, it has a contrary effect, and preserves from corruption. Pup. The value of medicinal salts I understand; they are employed as aperients; but pray what use is made of nitre ? - Tul. Nitre is frequently administered in medicine; and it is used very extensively in different arts. It is constantly used with common salt to preserve animal food. Immense quantities of it are required for purposes of war, as it forms one of the most important substances in gunpowder. 1'up, Teil me mow some of the mosi usefui of the metallic salts. a ul. They are, green vitriol (or copperas), blue vitrioj, and white vitriol. Green viiriei is used in inaking ink, and in dying woollen cloth and hats black. I:lue vitriol is also applied to dyeing, and to staining feathers, fowling-pieces, tea-urns. &c. White vitriol is used in medicine, and is employed in great quantities by varnishers to make their oil varnishes dry quickly. A fine white durable colour is also prepared form it. Pup. What particular minerals are included under the class of combustibles? Tut. Sulphur, naphtha, coal, resin, &c. Pup. In what maniier is sulphur employed? Tut. A considerable quantity is employed in making gunpowder, and in various processes of dyeing and calico-printing: it is occasionally administered in medicine, &c. Pup. Of what useis naphtha ?