CHEMISTRY. 



51 



Composi- 

 tion ac. 

 cording to 

 Davy. 



Elements flame. This mixture, according to Fourcroy, deto- 

 of nates when passed through a red-hot tube. 



Neither azote nor muriatic acid produce any effect 

 "*"Y"^ upon it. 



Several of the metals decompose it. When kept 

 for some time in contact with iron, its bulk dimi- 

 nishes, and it is converted into nitrous oxide. 



It is absorbed unchanged by a solution of green 

 sulphate or muriate ot iron. The liquid acquires a 

 deep brown colour, and, when kept, becomes blue. 

 The gas may be expelled unaltered by heat. 



The following bodies convert this gas into nitrous 

 oxide. Alkaline sulphites, hydrogureted sulphurets, 

 muriate of tin, sulphureted hydrogen gas, iron or 

 zinc filings moistened with water. 



From the analysis of Mr Davy, it appears to be 

 composed by weight of 



57 oxygen. 

 43 azote. 



10O 



Compoti- According to Gay Lussac, nitrous gas is compo- 

 tion ac- ed of equal bulks of oxygen and azotic gas united 

 cording to together, and its specific gravity is exactly the mean. 

 Hence no change of bulk takes place when they are 

 combined. This would give us nitrous gas composed 

 by weight of 53 oxygen. 



47 azote. 



10O 



CHAP. V. 



Of Acids. 



Acids. THE word acid, originally synonymous with lour, 



is at present applied to all bodies possessed of the 

 following properties : 



1. When applied to the tongue, they excite that 

 sensation which is called sour or acid. 



2. They change the blue colours of -vegetables to 

 red. 



3. They unite with water in almost every proportion. 



4. They combine with the alkalies, earths, and 

 metallic oxides, and form a class of bodies called sails. 



Every acid does not possess the whole of these 

 properties. But all of them possess a sufficient num- 

 ber to distinguish them from other bodies. The 

 second and fourth properties are considered as the 

 most important and essential. 



It was at one time tx-lievcd, that there existed only 

 one acid in nature, and that all bodies owed their 

 acidity to the presence of that acid. 



This notion was long a favourite one among che- 

 mists, and sulphuric and phosphoric acids were pitch- 

 ed upon as the universal acids. But the claims of 

 neither could stand the test of a rigid examination. 

 At last Mr Lavoisier proved, that many substances 

 were capable of combining with oxygen, and by that 

 means were converted into acids. Hence oxygen 

 was termed the acidifying principle. 



All that can be meant by tins appellation, is only 

 that many aci<!s contain oxygt-u ai> a constituent, and 

 lhat, when deprived of oxygen> they low their aad 



characters. In this sense the appellation is correct Elements 

 enough. But it is not true that oxygen itself pos- ' 

 sesses acid characters ; neither has it been proved ._,- I "' s _j--' 

 that it exists in every acid. Many substances contain 

 oxygen which are entirely destitute of acid proper- 

 ties. Thus water, alkalies, and alkaline earths, con- 

 tain it. Yet it would be absurd to consider any of 

 these bodies as acids. As the acids are very nume- 

 rous, and very heterogeneous in their properties, it 

 will be of some importance to subdivide them into 

 classes. They may be arranged under three heads : 

 1. Acid products; 2. Acid supporters ; 3. Combu- 

 tible acids. 



CLASS I. Acid Products. 



All the acids belonging to this class possess the Acid pro. 

 following properties : 



1. Thry may be formed by combustion. Of course 

 their base is a simple combustible. 



2. They are incombustible. 



3. They resist a violent heat without decomposi- 

 tion. Rut to this there are some exceptions. 



4. They are dec mposed by the joint action of a 

 combustible body and caloric. 



5. Oxygen is an essential ingredient in all of them. 

 Some of the combustibles combine with two doses 



of oxygen, and form two distinct acids. When that 

 happens, the acid containing the smallest dose of oxy- 

 gen is distinguished by the termination oils, while 

 that which contains a maximum of oxygen is distin- 

 guished by the termination ic. Thus sitlphurous and 

 sulphuric acids. The first contains the least, and the 

 second the most oxygen. 



The following Table exhibits the names of the Table of 

 acid products, their bases, and the proportion of oxy- acid pro- 

 gen in each, combined with 100 of the bases as far ducts, &*. 

 as it is known at present. 



SECT. I. Of Sulphuric Acid. 



Sulphuric acid seems to have been discovered by Sulphuric 

 the alchymists. It was long obtained by distilling acitl ' 

 the salt called green vitriol, or sulphate of iron. 

 Hence the name* oil of vitriol and vitriolic acid ori- 

 ginally applied to it. It is now procured by burn- HOW oi 

 ing a mixture of sulphur and nitre in chambers lined tained. 

 with lead, the bottom of which ij covered with wa- 



