372 HISTORY OF SCIENCE. 



three elements, calcium, carbon, and oxygen ; but according to La- 

 voisier's views, the oxygen enters into the compound on two different 

 footings, one part attracted to the metal calcium, the other forming 

 the acid by union with carbon. The constitution of carbonate of lime 

 according to this view is dualistic, and may be represented thus : 

 carbon \ . < calcium, 

 oxygen > \ oxygen, 



whereas the results of final analysis may be more simply indicated 

 thus: carbon+oxygen+calcium. 



Much discussion has subsequently been raised as to the merits of 

 the dualistic and the unitary method of considering the composition 

 of salts and other compounds which correspond respectively with the 

 formulae given above. These discussions have sometimes been raised 

 on a false issue, namely, the actual and inner constitution of matter, 

 whereas all that the chemist's knowledge can compass is a knowledge 

 of reactions ; and the Lavoisier conception of salts prevails to this day 

 simply because it corresponds with the more common reactions in 

 which salts are concerned. 



Lavoisier considered oxygen as the sole acidifying principle, but it 

 was soon remarked that oxygen is altogether absent from certain 

 bodies which possess undeniable acid or base-saturating properties, 

 such -as Prussic acid, for example. Then there was the case of muri- 

 atic acid already mentioned (page 367) ; but though oxygen had not 

 actually been obtained from this last body, it was held to be never- 

 theless an oxygenated compound until Davy showed its true character. 

 One result of Davy's discoveries has been an important change in the 

 views of chemists regarding acids : oxygen is no longer regarded as the 

 essential acidifying principle. The name of acid is given only to sub- 

 stances which contain hydrogen and are capable of neutralizing bases. 



A tabular view of the chemical elements and their binary combi- 

 nations with oxygen, from Kerr's English translation of Lavoisier's 

 "Elements of Chemistry" (Fourth Edition, Edinburgh, 1799), will 

 serve to give the reader a general view of the scope of chemical science 

 at the close of the eighteenth century. 



SIMPLE SUBSTANCES. 



Light, caloric, oxygen, azote (nitrogen), hydrogen. 



Oxidizable and acidifiable non-metallic substances. Sulphur, phosphorus, carbon, 

 muriatic radical, fluoric radical, boracic radical. 



Oxidizable and acidifiable metallic bodies. Antimony, arsenic, bismuth, cobalt, 

 copper, gold, iron, lead, manganese, mercury, molybdenum, nickel, platina, silver, tin, 

 tungsten, zinc. 



Salifiable earthy siibstances. Lime, magnesia, barytes, alumina, strontia. 



COMPOUND OXIDIZABLE AND ACIDIFIABLE RADICALS. 



Mineral. The radical of muriatic acid. 



Vegetable. The radicals of tartaric, malic, citric, pyrolignic, pyromucic, oxalic, acetic, 

 succinic, benzoic, camphoric, and gallic acids. 



Animal. The radicals of lactic, saccho-lactic, formic, bombic, sebacic, lithic, and 

 Prussic acids. 



