System of Chemistry, by Prof. Berzelius. 69' 



following definition, " the combustible body contained in an acid, or 

 in a salifiable base, is called the radical of the acid, or of the base.^^ 

 In the second vol. p. 163, he defines hydracids to be "those acids, 

 which contain an electronegative body, combined with hydrogen ;" 

 and in the next page it is stated, that " hydracids are divided into 

 those which have a simple radical, and those which have a compound 

 radical. The second only comprises those formed with cyanogen 

 and sulphocyanogen." Again, in the next paragraph, " no radical is 

 known that gives more than one acid with hydrogen, although sul- 

 phur and iodine, are capable of combining with it in many propor- 

 tions. If at any future day more numerous degrees of acidification 

 with hydrogen, should be discovered, their denomination might be 

 founded on the same principles as those of oxacids." Consistently 

 with these quotations, all the electronegative elements forming acids 

 with hydrogen, are radicals, and of course by his own definition, 

 combustibles ; while hydrogen is made to rank with oxygen as an 

 acidifying principle, and consequently is neither a radical nor a com- 

 bustible. Yet page 189, vol. 2d, in explaining the reaction of fluo- 

 boric acid with water, in which case, fluorine unites both with hydro- 

 gen and boron, it is mentioned as one instance among others in which 

 fluorine combines with two combustibles. 



I am of opinion that the employment of the word hydracid, as co- 

 ordinate with oxacid, must tend to convey that erroneous idea, with 

 which, in opposition to his own definition, the author seems to have 

 been imbued, that hydrogen in the one class, plays the same part as 

 oxygen in the other. But in reality, the former is eminently a com- 

 bustible, and of course the radical, by his own definition. 



Dr. Thomson, in his system, does not recognise any class of acids, 

 under the appellation of hydracids ; but with greater propriety, as I 

 conceive, places them under names indicating their electronegative 

 principles. Thus he arranges them as oxygen acids, chlorine acids, 

 bromine acids, iodine acids, fluorine acids, cyanogen acids, sulphur 

 acids, selenium acids, and tellurium acids.* Those appellations 

 might, I think, be advantageously abbreviated into oxacids, chlora- 

 cids, fluacids, bromacids, iodacids, cyanacids, sulphacids, selenacids, 

 telluracids. 



As respects the acids individually, I conceive that it would be pre- 

 ferable, if the syllable indicating the more electronegative element 



* I had formed my opinions on this subject, before I was aware that Dr. Thomson 

 had resorted to this classification. 



