A pure carbonate of potassa may be also prepared by fusing pure nitre in an earth en crucible, and projecting charcoal into it by small bits at a times till it ceases to cause deflagration. Or a mixture of 10 parts of nitre and 1 of charcoal may be deflagrated in small successive portions in a redhot deep crucible. When a mix • ture of 2 parts of tartrate of potassa, or crystals of tartar, and 1 of nitre, is defla grated, pure carbonate of potassa remains mixed with charcoal, which by lixiviation, and the agency of quicklime, will afford a pure hydrate. Crystals of tartar calcin ed alone yield also a pure carbonate. Caustic potassa may be crystallized ; but in genera•it occurs as a white brittle substance of spec. gray. 1.708, which melts at a red heat, evaporates at a white heat, deliquesces into a liquid in the air, and attracts carbonic acid ; is soluble in water and alcohol, forms soft soaps with fat oils, and soapy-looking compounds with resins and wax ; dissolves sulphur, some metallic snlphurets, as those of antimony, arsenic, &c., as also silica, alumina, and certain other bases ; and decomposes animal textures, as hair,wool, silk, horn, skin, &c. It should never be touched with the tongue or the fingers.
The only certain way of determining the quantity of free potassa in any solid or liquid, is from the quantity of a dilute acid of known strength which it can sa turate.
The hydrate of potassa, or its ley, often contains a notable quantity of carbonate, the presence of which may be detected by lime water, and its amount he ascertained by the loss of weight which it suffers, when weighed portion of the ley is pour ed into a weighed portion of dilute sul phuric acid poised in the scale of a balance.
Carbonate of potassa is composed of 48 parts of base, and 22 of acid, according to most Britsh authorities ; or, iu 100 parts, of 68-57 and 81-43; but according to Berzelius, of 68-09 and 31-91.
Carbonate of potassa, as it exists asso ciated with carbon in calcined tartar, passes very readily into the Bicarbonate on being moistened with water, and having a current of carbonic acid gas passed through it. The absorption takes place so rapidly, that the mass becomes hot, and therefore ought to be surrounded with cold water. The salt should then be dis solved in the smallest of water at 120° F., filtered, and crystallized. The exports of potash for the years 1847-48 was—in 1847, 618,000 dollars ; in 1848, 466,477. The quantity in value which came to the Hudson River, on all the canals, was—in 1846, ashes, barrels, 46,812, value, 1,076,904; in 1847, ashes, barrels, 37,538, value, 1,135,288.