1820.] Dr. Macneven on the Atomic Theory. 289 



Article VIII. 



Exposition of the Atomic Theory of Chemistry; and the Doctrine 

 of Definite Proportions. By William James Macneven, M.D. 

 Professor of Chemistry and Materia Medica in the College of 

 Physicians and Surgeons of the University of the State of 

 New- York. 



(Continued from p. 214.) 



45. Potassium. — It follows from a comparison of the experi- 

 ments of Davy, Gay-Lussac, Thenard, and Berzelius, that pure 

 potash is a binary compound of 100 potassium and 20 oxygen 

 by weight ; and as in this compound, being the lowest, one atom 

 of potassium combines with one atom of oxygen, these respec- 

 tive atoms will be in the same proportion, i. e. 



Ox. Potas. A I. ox. 



20 : 100 :: 1 : 4 weight of the atom potassium. 



Again, Gay-Lussac and Thenard have shown that the peroxide 

 of potassium is composed of 100 potassium and 60 oxygen ; or 

 three times the quantity in the protoxide ; therefore oxygen 

 combines with potassium in the proportion of 1 to 3, showing 

 the peroxide as a compound of 1 potassium + 3 oxygen. 



46. Barium. — The base of baryta may be determined from 

 the combination of baryta with sulphuric and carbonic acids. 



Sulphate of baryta is composed of acid 100 + 194 base, and 

 the carbonate of acid 100 -i- 354-54 base. Now, according to 

 a canon of Berzelius deduced by him from numberless experi- 

 ments, whenever a base and an acid combine, the oxygen in the 

 acid bears a fixed relation to the oxygen in the base. One hun- 

 dred parts by weight of sulphuric acid will saturate a quantity of 

 base, containing 20 parts oxygen; 100 parts carbonic acid 

 will saturate a quantity of base containing 36*26 parts oxygen. 

 Hence 194 parts baryta, which combine with 100 sulphuric acid, 

 contain 20 oxygen ; and 354-54 baryta, which combine with 100 

 carbonic acid, contain 36-267 parts oxygen. To obtain the pro- 

 portion of oxygen in 100 of baryta from these data we say, as 

 194 baryta : 20 oxygen :: 100 baryta : 10*309 oxygen. And as 

 354-54 baryta : 36-267 oxygen :: 100 baryta : 10*2 oxygen. The 

 mean of these (10-269) is the oxygen in 100 of baryta; and if 

 the oxygen be 10*269, the barium is 89*731. Reducing these 

 numbers to their lowest terms, if the atom of oxygen be 1, the 

 proportional weight of the atom of barium will be 8*73. 



47. Cdlcium, as far as yet known, combines with only one pro- 

 portion of oxygen, and forms the important oxide of lime. It is 

 from the sulpiiate and carbonate that we can best arrive at the 

 composition of lime, and this method admits of considera bl 

 accuracy. 



Vol. XVI. N° IV. T 



