i 



On the Oiigin of the Aloimc Theouj. 411 



the acid contained twice as much oxygen as the base, this was 

 u proof that the acid contained two atoms of oxygen ; if it con- 

 tained thrice as much, it contained three atoms of oxygen ; and 

 so on. Thus in the sulphates the sulphuric acid contains three 

 times as much oxvgen as the quantity of base which it saturates. 

 Hence we infer that sul])huric acid is a comj^ound of one .atom 

 of sulphur and three atoms of oxygen. In the sulphites the acid 

 contains twice as much as the base which it saturates. Hence 

 we infer that sulphurous acid is composed of one atom of sul- 

 phur and two atoms of oxygen." 



This is a singular mode of ascertaining the quantity of oxygen 

 in the sulphuric and sulphurous acids. 



I have proved, in mv Comparative View, that sulphuric acid 

 consists of one ultimate particle of sulphur aiul two of oxygen ; 

 and that sulphurous acid consists of one and one of its con- 

 stituents. 



I have also ascertained that a fresh-made solution of sulphate 

 of iron contains in the molecule one ultimate particle of iron, 

 three ultimate particles of oxygen, and one of sulphur, and that 

 one-third of the oxygen was supplied by the water. 



I will quote the following lines, taken from my Comfjaraliue 

 View, on this subject*. 



" When potash in solution is poured into a solution of sul- 

 phate of iron, immediate decomposition takes place, sulphate 

 of pota«h is formed, and the iron is disengaged of a darkish blue 

 colour, united with one-third the quantity of oxygen necessary 

 to its perlcct oxidation f. The iron could not receive this oxy- 

 gen from the sulphuric acid being found united to the alkali 

 in its perfect state, otherwise we should obtain a sulpliite of 

 potash." 



When the solution of sulphate of iron is exposed to atmo- 

 spheric air it attracts oxygen, and acquires a yellowish-brown 

 colour. This oxvgen must unite to the iron, the sulphuric acid 

 having no affinity whatever to oxygen. During this process a 

 vellov/ oxide is thrown down, which 1 thought at the time I 

 wrote mv Comparative View was occasioned by an union of car- 

 bonic acid to a portion of the oxide, in consequence of the weak 

 affinity of the dentoxide of iron to the sulphuric acid. I also 

 .supposed that the acid of the oxide deposited must have been 

 in a free state in the solution of the sulphate, particularly as the 

 sulphate exposed to the operation was as neutral as a solution 

 of a metal in an acid could be made. 



But on inquiring into this affair more closely, I found that the 



* Sec Tiiy Atomic Tlicory, paj;cs 70 and 71. 



t At tliiit period (1788) 1 lljou(;lit ilicri; wtic tiirce oxides of iron; no- 

 thing has occurred since lo induce me to alter my opinion. 



oxysulphatc, 



