moving the bottle from the trough the gas will be seen to turn red on mixing with the air. It unites with oxygen, forming hyponitric acid (NO). Evaporate the blue solution in a dish till it is syrupy, then cool, when it will set to a crystalline mass of cupric nitrate. Take a small quantity of this, and ignite on a platinum capsule till it has turned entirely black. The following change takes place: Cu(NO), Cupric nitrate = CuO + 2NO. + 0 Cupric Hyponitric acid The black residue is cupric oxide. The green substance which is formed intermediately is a compound of cupric nitrate and oxide, and is called basic cupric nitrate. Take a small quantity of the oxide, put it in a hole scooped in a piece of charcoal, put on it a small lump of potassic cyanide, and heat with the blowpipe. The copper will be at once reduced in the form of a spongy mass, which may be melted into a globule by further heat. 15. HYDRIC NITRATE ON HYDRIC CHLORIDE. Put a little hydric chloride in a test tube, and add about a fourth of hydric nitrate. This mixture is called nitrohydrochloric acid or aqua regia. Warm it, when chlorine and hyponitric acid will escape. It is used for dissolving gold and platinum and a few compounds, and acts through the free chlorine which it gives. 16. HYDRIC NITRATE ON FERROUS SULPHATE. Put a crystal or two of ferrous sulphate in a test tube, add some water and a little hydric sul D phate and boil. A colorless solution will be obtained. Now add a drop of hydric nitrate, when the following change will be effected : The nitric oxide dissolves in the excess of ferrous sulphate to a dark fluid. Add another drop of hydric nitrate, and so on, when all at once the above change being completed, all the ferrous sulphate will have been converted into ferric sulphate, which is incapable of dissolving nitric oxide, and this will escape with sudden effervescence. The above reaction is utilized as a test for a nitrate, the experiment being made as follows:Powder a crystal of ferrous sulphate, and shake it up in a test tube with half an inch of cold water, when dissolved, add a minute quantity of the solution to be tested (take a drop of solution of potassic nitrate), and holding the tube slanting pour down the side carefully half an inch of hydric sulphate, so that it may form a layer at the bottom without mixing. A dark color will soon be apparent at the top of the hydric sulphate, which is rendered more evident by very gently shaking the tube, not mixing the fluids. ACTION OF ALKALIES ON ACIDS. The alkalies are potash (KHO), soda (NaHO), and ammonia (NH). The first two are solids, the last a gas; all are very soluble in water. They have a very strong taste, and turn litmus paper blue. Acids, on the contrary, turn litmus paper red. And if an alkali and an acid are mixed in proper proportion, the mixture will be neutral like water, that is, it will not affect litmus. 17. POTASH ON HYDRIC SULPHATE. Dissolve a lump of potash in water in a Berlin dish. Now lay several strips of litmus paper on the bench side by side. Add some dilute hydric sulphate to the potash, stir with a glass rod, and then touch one of the strips of litmus with the rod. If the litmus turns blue, add more acid and so on, till the neutral point is gained. The following change will have taken place: H.SO + 2KHO = K.SO 2 2H,0 The solution now tastes neither acid nor alkaline, but saline. Evaporate somewhat and set aside, when small sparkling crystals of anhydrous potassic sulphate will be formed. The mother liquor may be thrown away, and the crystals dried on blotting paper. If hydric sulphate is half neutralized by potash, thus H.SO Hydric sulphate + KHO = Potash KHSO + H2O Hydropotassic sulphate we get hydropotassic sulphate, the same substance which was left in the retort after making nitric acid. This is strongly acid to the taste and litmus. To do this experiment the proper way is to take a certain quantity of hydric sulphate, divide it in half, neutralize one-half and add the other half. 18. POTASH ON HYDRIC CHLORIDE. Dissolve some potash in water, and neutralize with hydric chloride. The following change takes place: HCI + KHO = KCI + H2O Evaporate to dryness, and potassic chloride will be left as a saline mass. 19. POTASH ON HYDRIC NITRATE. Dissolve some potash in water, and neutralize with hydric nitrate. The following change takes place: Evaporate somewhat and crystallize. We have thus reconverted the hydric nitrate into potassic nitrate, from which it was originally made. 20. SODA ON HYDRIC SULPHATE, H. CHLORIDE AND H. NITRATE. The action is exactly similar to that of potash on these acids. The equations are the same, substituting Na for K. The crystals of sodic sulphate are large, and consist of Na,SO,.10H2O. In making sodic chloride, you will notice the reconversion of hydric chloride into the substance from which it was originally obtained. AMMONIA ON HYDRIC SULPHATE, H. CHLORIDE, AND H. NITRATE. [21. Ammonia gas.-As stated before, ammonia is a gas very soluble in water, having the composition NH.. What is usually called ammonia is the solution. The gas is most readily obtained by simply boiling the solution. Take a small flask and fit a gas delivery tube to it. Put in it some of the strongest solution of ammonia (s.g. 880), heat gently, and collect the gas in a dry sodawater bottle by upward displacement, allowing the gas to escape into the air for some time after the bottle seems full, so as to make sure that the bottle is completely filled with the gas. Now take away the lamp from the flask, and without delay remove the delivery tube carefully, covering the mouth of the bottle with the hand. Hold the bottle mouth downwards in water, and then remove the hand covering the mouth. The water will rush up and fill the bottle-that is, so far as the air has been expelled. A like experiment was made with hydric chloride, which also is a gas very soluble in water.] The action is exactly similar to that of potash on these acids. The equations may be written thusH2SO + 2NH, 4 = (NH,),SO. Ammonic [Ammonium hypothesis.-Inasmuch as ammonia behaves with acids like potash and soda, we assi |