3o8 HISTORICAL INTRODUCTION TO CHEMISTRY CHAP. 



Accuracy of the law of multiple proportions. The 



measurements of Stas provide two opportunities of testing 

 the exactness of the law of multiple proportions. 



(1) Dumas and Stas, in 1841 (see above, p. 148), showed 

 that 100 parts of carbonic anhydride contain 



carbon 27 '27 per cent., 



oxygen 72 '73 per cent. 



Stas, in 1849 ( see above, p. 151), showed that 224*683 

 grams of carbonic oxide combined with 128*367 grams of 

 oxygen to form 353*050 grams of carbonic anhydride. 

 Therefore, TOO parts of carbonic anhydride contain 



carbonic oxide 63 "64 per cent. 



oxygen 36 '36 per cent. 



Thus 27*27 grams of carbon unite with 72*73 grams of oxygen 

 to form 100 grams of carbonic anhydride, and with 

 63*64 27-27 = 36-37 grams of oxygen to form 63-64 grams 



of carbonic oxide. The ratio ? 2 ' ?3 = 1/9997. This ratio 



36-37 



differs from the integral ratio 2 : i by only one part in 7000 

 or 0*015 P er cent. 



(2) Stas's analysis of silver sulphate (Works, I. 410) 

 showed that it contained 69*203 per cent, of silver, united 

 with 69*203 x 14*852 -i- 100= 10*278 per cent, of sulphur and 

 100-69-203 10*278 = 20-519 per cent, of oxygen. In 

 the sulphate, then, 100 parts of silver are united with 

 20-5 19 -"-69-203 x ioo = 29'650 parts of oxygen. 



A second relationship between oxygen and silver is 

 afforded by the fact that 100 parts of silver were precipi- 

 tated by 69*103 parts of potassium chloride, which could be 

 derived from potassium chlorate containing 60*846 per cent, 

 of the salt and 39*154 per cent, of oxygen; 69*103 parts 

 of chloride would therefore combine with 



69 1 03 x 391? 54 = 44467 



60*846 

 parts of oxygen. 



