102 LETTEES OF BERZELIUS 



of iodine paper are exposed to moist atmospheric 

 air saturated with nitrous acid vapours, or suspended 

 in a flask, the bottom of which is covered with a 

 mixture of water and nitrous acid. 



I suspect that there exists a compound consisting 

 of N0 2 -fH0 2 , which when it comes in contact with 

 iodine gives up to it its H0 2 . According to your 

 view we must assume that when ozonized oxygen 

 combines with iodine, bromine and chlorine it is as 

 ozone that it does so. 



With regard to my views on the hydrate of nitric 

 acid, I venture to maintain that it is by no means 

 isolated and without analogy, so long as one holds 

 similar views on other acids. Anhydrous sulphuric 

 acid for example I regard as S0 2 + 0, the third 

 atom of oxygen being in a chemically active state ; 

 the hydrate of sulphuric acid I look upon as 

 S0 2 +H0 2 , and the normal sulphates as S0 2 +E0 2 ; 

 the hydrate of chloric acid would of course be 

 C10 4 +H0 2 , anhydrous iodic acid I0 4 +0 etc. 

 Possibly we might also regard the so-called first 

 hydrate of oxalic acid as 2CO-fH0 2 , acetic acid as 

 C 4 H 4 + 20 or as C 4 H 3 + H0 2 . However, I am always 

 suspicious about substances which cannot be isolated 

 and which cannot exist except in combination with 

 other substances, such as water and the so-called salt- 

 bases. I am half inclined to fear that the assumption 

 of these hypothetical compounds has retarded rather 

 than promoted the progress of chemistry. 



I have taken the liberty of giving you some of my 

 views on the different conditions of oxygen in the 



