206 Dr. Playfair on Transformations 



kali, although in a free state, the sulphur exhibits a superior 

 affinity, as shown by the decomposition which then results, 

 NO4S = NO + SO3. Now any substance which acts as an 

 accessory to the sulphur by aiding the withdrawal of oxygen 

 from the nitrogen decomposes it. This instability is especially 

 exhibited in NH4O, NO4S ; the 3 atoms of hydrogen of the 

 ammonia in their attraction for oxygen introducing another 

 affinity, which accelerates decomposition. And, in fact, we 

 do find that the same agents which so readily decompose the 

 oxygenous compounds, chloride of lime and peroxide of hy- 

 drogen, do equally cause the disruption of nitrosulphate of 

 ammonia into protoxide of nitrogen and sulphate of ammonia. 

 Alkalies are an exception to this rule, as they render the ni- 

 trosulphates more stable, while they make the peroxide of hy- 

 drogen prone to decomposition ; but the cases are different, 

 the latter substance having none of the properties of an acid. 

 The basic character of alkalies, defined as their power of 

 uniting with more oxygen, or with an acid playing the part 

 of an oxygenous element, is illustrated by several curious 

 decompositions. Thus, though grape-sugar reduces sulphate 

 of copper with ease, cane-sugar alone does not readily do so, 

 but M'hen mixed with potash and boiled with the salt, sub- 

 oxide of copper is produced, as in the mode of preparation 

 of that oxide suggested by Boettger*, or the reduction of 

 chloride of silver as proposed by Levolf. Here the disposi- 

 tion of the organic matter to unite with oxygen is able to 

 gratify itself when aided by the accessory affinity of the pot- 

 ash for oxygen. That the potash in this state acts by aiding 

 the oxidation, is seen by heating CugO with a solution of 

 caustic potash, exposed to the air, when it oxidizes much 

 more rapidly than when boiled with water alone J. When 

 suboxide of copper is dissolved in ammonia it oxidizes with 

 surprising rapidity. In this instance the hydrogen of the 

 ammonia adds to its disposition as an alkali to absorb oxy- 

 gen. The quick oxidation is not merely due to the fact of 



♦ Ann. der Pharm. und Chemie, xxxix. 176. 



f Berzelius, Jahreshericht, vol. xxv. 



X This experiment may be simply made as follows : — Three shallow eva- 

 porating basins of the same size and form, each containing the same quan- 

 tity of suboxide of copper, are taken, and to one is added a solution of 

 potash or soda; to the second, a solution of chloride of manganese; to the 

 third, common water, taking care that the same volume of each fluid is 

 added. The whole are now placed on a sand-bath, so as to be exposed to 

 equal temperatures, and stirred occasionally. The suboxide of copper in 

 the basin containing chloride of manganese oxidizes very rapidly ; that in 

 contact with the potash more slowly; and that with simple water is scarcely 

 effected when both the others have lost their red colour. These actions are 

 strictly in accordance with theory. 



