On the Origin of the Alomk Theory. 413 



in iota to the ultimate particle of the iron, wjiich afforded it at 

 once oxygen of calcination and acid of solution. Tliis is a proof 

 that a molecule of nitrate of iron consists of five ultimate par- 

 ticles of oxygen, one of azote, and one of iron : or the (|uantity 

 of oxygen might he estimated higher, if we suppose that the par- 

 ticle of iron wa- supplied with one particle of oxygen at the ex- 

 pense of a portion of the sulphurous acid during the solution. 



This I am inclined to believe is the case, from the quantity 

 of sulphur disengaged in the operation. Tlie solution of nitrate 

 of iron when exposed to the air is affected lilce the sulphate of 

 iron ; it acquires a brownish yellow colour, and a copious yellow 

 oxide is deposited. 



The red oside of mercury is dissolved by nitric acid without 

 decomposition of any part of the latter, and the molecule must 

 contain seven of oxygen. These facts do not agree with Berze- 

 lius's doctrine of the relative proportions of oxygen in the bases 

 and acids of saline bodies. 



It was my opinion at the early period in which I brought 

 forward the Atomic Theory, that an ultimate atom of a metallic 

 oxide and an ultimate atom of an acid unite chemically, and that 

 these were their definite proportions. I am still inclined to 

 think that it is the case, with some exceptions, a few of which 

 are adduced above : yet it would not be contrary to the laws which 

 I established that atoms should unite 1 and 2, like the ultimate 

 particles of elementary matter. We know that sulphate of 

 potash will unite with two doses of sulphuric acid, that potash 

 will unite with two portions of acid of tartar, that potash will 

 also unite to two doses of oxalic acid, although the second dose 

 is so strongly attached in the above salts, that nothing but che- 

 mical means will separate them : yet it appears to me that it is 

 not a chemical utiion, particularly as those saline substances have 

 an acid taste. It is probably a kind of intermediate influence, 

 somewhat similar to what exists between saline substances and 

 water, or sugar and water, and gases and water, or alcohol and 

 water ; and the union which takes place between two neutral 

 salts is of a similar nature. 



The supposition tiiat two atoms of one substance will unite to 

 three atoms of another substance is contrary to the laws of the 

 Atomic System, as I have shown in my Comparative View, so 

 far as relates to the coinl)inations of the ultimate particles of 

 eletnentary matter ; and I should imagine that the same law ex- 

 tends to the combination of atoms, for atoms are as distinct or 

 insulated from ench otiier as j)articios. Thciefore 1 am inclined 

 to differ from the calculation of Dr. Thomson, that according to 

 ti)e analysis of ller/.elius of the sulphate of iron, it consists of 

 tv.o atoms of acid and three of oxide. Now one atom of the 



acid 



