436 Prof. Odling on the Natural Groupings 



in which condition only do they conduct electricity. Titanium, 

 like boron and silicon, is extremely infusible. 



Tin forms a prothydrate, SnO . H-0 ; a protoxide, SnO j and 

 a protochloride, SnCr^, &c. Titanium undoubtedly forms a 

 protoxide, which, like that of tin, is of a brown colour. There 

 is also some reason to believe that both silicon and boron form 

 protoxides. 



The members of this fourth group are remarkable for their 

 fluorine compounds. We have three simple fluorides, BF"*, SiF"*, 

 TiF'*. I have ascertained, moreover, that tin yields an analogous 

 compound, SnF"**. These fluorides are all formed by the action 

 of sulphuric acid and fluor-spar on the respective anhydrides. 

 The first two fluorides are gaseous, that of boron, and doubtless 

 that of silicon, being condensable ; the third is liquid, as is pro- 

 bably the fourth also. The three first fluorides unite directly 

 with ammonia. The composition of the silicic compound is 

 3NH^ . SiF'*t. The boric and titanic compounds have probably 

 similar formulae. The double fluorides are very numerous and 

 well defined. The acids or hydrogen compounds can be prepared 

 by the action of water on the simple fluorides, or by the action 

 of a solution of fluorhydric acid upon the anhydrides, bodies 

 which are scarcely attackable by any other reagent in the moist 

 way. The powerful tendency to the pi'oduction of these double 

 fluoric acids is very remarkable. The formulse are, — 



2HF . BF-* Boro-fluorhydric acid. 



2HF . SiF^ Silico-fluorhydric acid. 



2HF . TiF4 Titano-fluorhydric acid. 



2HF . SiF Stanno-fluorhydric acid. 



The ammonium salts can be prepared by acting on the ammo- 

 niaco-fluorides (2NlrP . SiF'*) with water, or by neutrahzing the 

 above acids with ammonia, or even by acting upon the fluoride 

 of ammonium with the anhydrides. The potassium salts are 

 analogous to the ammonia salts, and are formed by similar 

 processes. 



2NH4F . BF4 Boro-fluorides 2KF . BF-* 

 2NH4F . SiF-* Silico-fluorides 2KF . SiF^ 

 2NH4F.TiF4 Titano-fluorides 2KF . TiF'' 

 2NH4F.SnF4 Stanno-fluorides 2KF . SnF" 



* A mixture of fluor-spar, stannic oxide and sulphuric acid, when gently 

 heated in a platinum capsule, developes an abundance of opake vapours, 

 in which the presence of both tin and fluorine is readily to be detected. 



t This and all the succeeding formulae pertaining to the fourth group 

 are extracted from Watts's translation of Gmelin's ' Handbook,' only so far 

 modified as to correspond with the atomic values that I have adopted. 

 The description of the properties of the different compounds is derived trom 

 the same source, 



