386 HISTORICAL INTRODUCTION TO CHEMISTRY CHAP. 



of Cavendish (p. 95), and of Priestley (p. 95). The pro- 

 duction of water during the burning of spirit of wine was 

 frequently recorded, right up to the time of Lavoisier, who 

 in 1784 obtained 18 ounces of water by burning 16 ounces 

 of spirit (Works, II. 358). But these observations could 

 not be used to explain the composition of organic compounds 

 until the experiments of Lavoisier (p. 97) and Cavendish 

 (p. 113) had disclosed the composite character both of fixed 

 air and of water. When these substances had been proved 

 to be " oxide of carbon " and " oxide of hydrogen " respec- 

 tively, Lavoisier was in a position to describe correctly the 

 nature of combustible organic substances as compounds of 

 carbon and hydrogen ; indeed, some years before these 

 names were introduced, he had already (pp. 145-148) made 

 analyses to determine the proportions of carbon and hydro- 

 gen in spirit of wine, in wax, and in olive oil. In his 

 Elementary Treatise, published in 1789, Lavoisier was able 

 to enumerate the chief elements present in organic com- 

 pounds, usually in combination with oxygen : 



" I have already observed that, in the mineral kingdom, 

 almost all the oxidisable and-acidifiable radicals were simple ; 

 that, in the vegetable kingdom on the contrary, and above 

 all in the animal kingdom, there were scarcely any which 

 were composed of less than two substances, hydrogen and 

 carbon ; that often nitrogen and phosphorus were united 

 with them, and that there were produced radicals with four 

 bases" (Works, I. 147). 



Thus, "the acetic radical is formed by the union of 



of caustic alkali, the lime was precipitated, and the alkali was rendered 

 mild." 



(3) That "fixed air is the chief part of the elastic matter which 

 is formed in liquids in the vinous fermentation." 



(4) That the " deadly vapour of burning charcoal . . . must be fixed 

 air," since a piece of red-hot charcoal, inserted in the nozzle of a pair 

 of chamber-bellows, imparted to the air which passed over it the power 

 to render lime-water milky (Lectures, 1803, II. 87-88). 



These observations were not published for nearly fifty years, though 

 manuscript copies of the lectures (which can still be purchased) appear 

 to have been sold to the students by the lecture-assistant. 



