NITRO-MURIATIC ACID

Aqua regia ( Acide nitro-muriatique , Fr.; Salpeter-salzsaüre, Königswa er , Germ.); is the compound menstruum invented by the alchemists for di olving gold. If strong nitric acid, orange-coloured by saturation with nitrous gas (deutoxide of azote), be mixed with the strongest liquid muriatic acid, no other effect is produced than might be expected from the action of nitrous acid of the same strength upon an equal quantity of water; nor has the mixed acid so formed, any power of acting upon gold or platina. But if colourle aquafortis and ordinary muriatic acid be mixed together, the mixture immediately becomes yellow, and acquires the power of di olving these two noble metals. When gently heated, pure chlorine gas rises from it, and its colour becomes deeper; when further heated, chlorine still rises, but now mixed with nitrous acid gas. If the proce has been very long continued, till the colour becomes very dark, no more chlorine can be procured, and the liquor has lost the power of di olving gold. It then consists of nitrous and muriatic acids. It appears, therefore, that aqua regia owes its peculiar properties to the mutual decomposition of the nitric and muriatic acids; and that water, chlorine, and nitrous acid gas are the results of that reaction. Aqua regia does not, strictly speaking, oxidize gold and platinum; it causes merely their combination with chlorine. It may be composed of very different proportions of the two acids; the nitric being commonly of specific gravity 1·34; the muriatic, of specific gravity 1·18 or 1·19. Sometimes 3 parts, and at others 6 parts of the muriatic acid are mixed with 1 of nitric; and occasionally muriate of ammonia, instead of muriatic acid, is added to nitric acid for particular purposes, as for making a solution of tin for the dyers. An aqua regia may also be prepared by di olving nitre in muriatic acid. NITROUS ACID ( Acide nitreux , Fr.; Salpetrige sal peters aüre , Germ.), may be procured by distilling, in a coated gla retort, perfectly dry nitrate of lead, into a gla receiver surrounded with a freezing mixture. The acid pa es over in vapour, and condenses into a liquid; oxygen gas escapes through the safety tube; while oxide of lead remains in the bottom of the retort. Nitrous acid may also be obtained by distilling strong fuming nitric acid, at the lowest po ible temperature, and rectifying what comes over. At 4° -zero, Fahr., this acid is colourle ; at 32° it is wax yellow; at 60° it has an orange hue. It po e es a strong smell, has a very pungent, acrid, sour taste, and a specific gravity of 1·42. It powerfully decomposes organic bodies, staining them yellow. It boils at 82° Fahr. with the disengagement of red or orange fumes. Its constituents are, 41·34 of hyponitrous acid, and 58·66 of anhydrous nitric acid; or ultimately, 30·68 nitrogen = 1 volume, and 69·32 oxygen = 2 volumes. In its other habitudes, it is quite analogous to hyponitrous acid. A mixture of this double or compound acid with nitric acid, constitutes the orange-brown fuming nitrous acid of the British apothecaries. The hyponitrous and nitrous are two acids remarkable for containing no water in their composition; being therefore dry liquids .