262 On the TDefinite Proportions in which the [April, 



of lead. In the same manner I shall use the terms gu7)imates, 

 aiuylules, snccolactales, to denote the combinations of gum, starch, 

 sujjar of milk with saline bases. 



There is still a circumstance relative to the combination of the 

 ternary oxides with the saline bases, which deserves to be men- 

 tioned here. An excess of these V)ases, especially the stronger 

 ones, decomposes a great part of the ternary oxides in different 

 ways, usually producing a great quantity of carbonic acid. The 

 ternary oxides least exposed to this decomposition are these : 

 i. whose atoms of oxygen are equal in number to those of some 

 one of the other elements, or surpass them in number : and 

 2. when the ratio of the hydrogen to the oxygen is less than in 

 water. Such is the case with most of the acids analyzed. If the 

 atoms of carbon and hydrogen surpass in number those of oxygen 

 to a certain amount, the ternary oxide has a great tendency to 

 undergo decomposition from the action of the salifiable bases. 

 Sucli', for example, is the case with gallic acid, tannin ; and, to a 

 certain extent, with acetic acid. When, on the other hand, the 

 atoms of each of the combustible elements surpass four or five 

 times those of oxygen, the ternary oxide is more permanent : so 

 that those oxides are best preserved which have either a great ex- 

 cess of combustible atoms or ot oxygen. Of consequence, benzoic 

 acid and the fat oils arc but insensibly altered by the action of 

 alkaline bodies. 



This is the reason why, when the ternary oxides are gradually 

 decomposed, either by the influence of air and water, or of acids, 

 their atoms arrange themselves in such a manner as to form new 

 products, in which, on one side, the oxygen is in excess, and, on 

 the other, the atoms of the combustible elements greatly surpass 

 those of the oxygen. Thus sugar is converted into carbonic acid 

 and alcohol by fermentation ; and gallic acid, by the influence 

 of an alkali, yields on one side water and carbonic acid, and, on 

 the other, an extractive matter abounding in carbon, to which it 

 owes its dark colour. Perhaps it would be useful to class the ter- 

 nary oxides into : 1. Oxides not easily decomposed in consequence 

 of iluir excess of oxygen ; such as oxalic, citric, tartaric acids, &c. 

 2. Oxides easily decomposed in consequence of the equilibrium of 

 their elements, which is easily destroyed by a small force ; such as 

 tannin, gallic acid, sugar of milk, common sugar, iS:c. 3. Ox- 

 ides not easily decomposed in consequence of the excess of their 

 combustible atoms; such as benzoic acid, resins, fat oils, &c. 



Let us now turn our attention more particularly to the ternary 

 oxides destitute of acid properties. 



10. Common Sugar, 



I digested a solution of sugar with oxide of lead. At first the 

 oxide dissolved, but after the digestion had been continued for 

 pome time, it was converted into a l>glu white powder, by which 

 the whole liquid was rendered opake. I scjwratcd tlic white powder 



