184 Dr. Hare on certain points 



lie had endeavoured to establish. I stated that I did not 

 deem it necessary to appeal to his excellent observations, 

 proving certain attributes of acidity to exist in one case, those 

 of alkalinity in the other. I alleged my definition to be founded 

 on the conviction that the property of affecting vegetable co- 

 lours, on which that sagacious chemist lays so much stress, 

 has not, latterly, been deemed necessary in acids ; and that 

 in bases it never was required. As respects them, it only 

 served as a mean of subdivision between alkaline oxides and 

 other oxibases. 



I am at a loss to discover in what part of my letter there 

 was any language which could convey the erroneous impres- 

 sion, that, in defining acids and bases I proposed to overlook 

 properties, and to be regulated by attention to the number of 

 atoms in a compound. Certainly nothing was more foreign 

 to my thoughts. 



It is assumed by Berzelius that the saturation of the fluo- 

 base of potassium by fluohydric acid, cannot be considered as 

 analogous to the saturation of the oxybase of potassium by 

 sulphuric acid ; because the resulting compound is to the taste 

 in one case neutral, in the other sour. In reply I suggested 

 that if the salidity of the biborates and bicarbonates was not 

 to be questioned on account of their alkaline taste, nor that 

 of the protochloride of tin on account of its sourness, it was 

 not consistent that the pretensions to salidity of the fluohy- 

 drate of the fluobase of potassium should be denied on account 

 of its sour taste. I will now add that if the fluosilicate of po- 

 tassium be a double salt, the fluoride of silicon one of its two 

 constituents must be a simple salt, and yet it is sour. If a 

 simple salt may be sour, why may not a double salt have this 

 attribute; and how in fact can its presence be inconsistent 

 with salidity? Is not the absence of this characteristic in si- 

 lica and tannin, and many other acids, as much against their 

 claims to acidity, as its presence in other compounds is an 

 objection to their association with saline bodies ? It is consi- 

 dered by Berzelius an objection to the views which I have 

 espoused, that the halogen bodies, while forming acids with 

 various metallic radicals which oxygen does not acidify, do 

 not form acids with sulphur, phosphorus, and arsenic which 

 oxygen does acidify ; yet what is there in this, more difficult 

 to reconcile with the established results of chemical combina- 

 tions, than in the fact that oxygen forms with sulphur, phos- 

 phorus, and arsenic, strong acids, with hydrogen water; while 

 with hydrogen the halogen bodies all form compounds which 

 Berzelius describes as having the highest pretensions to 

 acidity ? The highly active acid properties of the fluorides of 



