1S20.] extracted from Piirites at Fahlitn. 21 



cals. Tliese facts lead v.s to presume that the hepatic taste and 

 smell, from being peculiar to sulphur, are common to that c^ass 

 of acid bodies, as well as to their combinations with bases ; and 

 that an hepatic taste and smell are as essential to the hydracida 

 and to then- combinations with alkalies, as the acid taste and 

 smell are to the strong oxacids, and the saline taste to their neu- 

 tral combinations with alkalies. I, therefore, think it very- 

 probable that an alkaline salt destitute of the hepatic taste does 

 not contain an hydracid ; and, on the contrary, if the taste be 

 sahne, that it contains an oxacid. By extending these consider- 

 ations still further, we find that tlie oxacids, whose names termi- 

 nate in oiis, give to their alkaline salts a peculiar taste by which 

 we recognise the acid ; for example, the sulphites and the phos- 

 phites. Further, another class of oxacids very weak, and very 

 indistinctly acid, as the tungstic and antimonic acids, the oxide 

 of tellurium, &.c. give to their compounds with the alkalies a 

 metallic taste ; so that each class appears to have general 

 common properties by which the class can in some measure be 

 known . 



Chlorine and iodine combine likewise v.ith hydrogen ; but 

 these combinations are very strong acids, and have their taste 

 and smell purely acid. These acids have the peculiar property 

 of being able to reduce, by means of their hydrogen, potash and 

 soda, and of forming chlorides and iodides, whose pure saline 

 taste is entirely analogous with the combination of the strong 

 oxacids with tlie alkalies. On the other hand, the hydrogen of 

 these acids does not reduce the oxides of copper, bismuth, gold, 

 &c. with which the hydrochloric and hydriodic acids combine 

 without decomposition. Thus we perceive that the analogy of 

 these hydracids Avith those of which we have just spoken is 

 entirely null. I thought it proper not to omit these comparisons, 

 because they constitute an addition to the circumstances, which 

 sooner or later will give us more satisfactory information respect- 

 ing the nature of muriatic, iodic, and fluoric acids. 



We have seen the great analogy betvi'een sulphurand selenium, 

 and this analogy continues even in their combinations with 

 oxygen; so that both form acids but little volatile. However, 

 these acids have not the same analogy with each other as the; • 

 radicals have. Sulphuric acid belongs to that numerous class of 

 acids which have three atoms of oxygen, and possesses in con- 

 sequence the manner of combination of these acids. Selenic 

 acid, on the contrary, belongs to the small class of acids which, 

 without terminating in ous, contain only two atoms of oxygen; 

 and in this respect has a strong analogy with carbonic and 

 boracic acids. Like these acids, it does not form neutral salts 

 with alkalies. In the salt, in which the acid contains twice as 

 much oxygen as the base, the alkali re-acts ; and in those in 

 which the acid contains four times as much oxygen as the base, 

 it is the acid which re-acts. We find the same phenomenon in 



