22 GRAHAM LUSK 



the heat rays of a large burning glass and produce ''fixed air" and "fire air" 

 from them. Ten days after his conversation with Priestley, and again 

 during the month of the following March, Lavoisier went to Montigny to 

 visit his friend Trudaine, who was the owner of an immense burning 

 glass 42 ins. in diameter, which had cost 15,000 livres (about $3,000), 

 and he here repeated Priestley's experiments. In the paper read before 

 the Academic des Sciences at Easter, 1775, Lavoisier (a) stated that he 

 took the red mercury calx and heated it with carbon and obtained "fixed 

 air," and when he heated the same without carbon a gas was evolved in 

 which a flame burned with the splendor of phosphorus in air, and that this 

 gas was the "air eminently respirable." The loss in weight of the mercury 

 calx was equal to the weight of the "air eminently respirable" given off. 

 He concluded that "fixed air" was the result of the union of carbon with 

 "air eminently respirable." In a subsequent paper he reported that it was 

 this "air eminently respirable" which was absorbed by phosphorus and 

 sulphur when they burn with the production of phosphoric and sulphuric 

 acids (6). 



Having discovered these facts, Lavoisier (c) proceeded to determine the 

 effect of a sparrow upon the content of air in a confined space. In a 

 brief memoir published in 1777 he enunciated the principles that during 

 respiration it was only "air eminently respirable" (oxygen) which dis- 

 appeared from the atmosphere when an animal was put into a confined 

 space and that this air was supplanted by expired "aeriform calcic acid" 

 (carbon dioxid) ; that when metals were calcined in air oxygen was 

 absorbed until its supply was exhausted; that if after an animal had 

 perished in a confined space and the carbon dioxid in the atmosphere was 

 absorbed by alkali the "foul air" remaining was the same kind of air as 

 that found after metals had been calcined in air in an Inclosed space. 

 All the former qualities of this air could be restored by adding to it "air 

 eminently respirable." 



Three years later Lavoisier and La Place made another step in ad- 

 vance. (Lavoisier and La Place, (n) 1780.) They noticed that a guinea- 

 pig produced 224 grains of carbonic acid in ten hours, and that what would 

 now be called the respiratory quotient was 0.84. Then they put another 

 guinea-pig in their recently constructed ice calorimeter and found that 

 the heat given off by the animal melted 13 oz. of ice in a period of 10 

 hours. Next they calculated that if carbon was oxidized so that 224 

 grains of carbonic acid were produced, 10.4 oz. of ice would have been 

 melted. They realized that in the case of the guinea-pig allowances would 

 have to be made (1) because the legs of the animal became chilled during 

 the experiment; (2) because the water of respiration was added to that of 

 the melted ice; and (3) because the influence of cold increased the heat 

 production of the animal. But tney nevertheless stated that "Since we 

 have found in the preceding experiments that the two qualities of heat 



