Chemistry and Physics. 247 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. Silicon-flu or o form. — By the action of silicon-chloroform 

 upon tin and titanium fluorides, Ruff and Albert have suc- 

 ceeded in preparing the hitherto unknown silicon-fiuoroform, 

 SiHF 3 . Titanium fluoride is preferable to the tin compound for 

 the preparation of the new compound. The reacting substances 

 were heated in a copper bomb or in a well dried sealed-tube of 

 glass for 18 hours at 100-120°, and the resulting product was 

 collected by condensing with liquid air. The reaction is as 

 follows : 



3TiF 4 + 4SiHCl 3 = 4SiHF 3 + 3TiCl 4 . 

 Silicon-fiuoroform is a colorless gas which forms a liquid boiling 

 at —80° and solidifying at about —110°. When brought into 

 contact with sodium hydroxide solution it is decomposed with the 

 liberation of an equal volume of hydrogen, according to the 

 equation 



SiHF 3 + 3NaOH + H 2 = Si(OH) 4 + 3NaF + H 2 . 



When heated in a closed tube to about 420° the gas is decom- 

 posed with deposition of silicon as follows : 

 4SiHF 3 = 2H 2 + 3SiF 4 + Si. 



It is combustible in the air, and forms explosive mixtures with 

 the same, possibly according to the equation 



12SiHF 3 + 60 2 = 3SiF 4 + 3Si0 2 + 4H 2 SiF 6 + 2H 2 Si0 3 . 

 The preparation of silicon-fiuoroform completes a series of halo- 

 gen compounds in which the boiling-point rises rapidly with the 

 atomic weight of the halogen as follows : 



Compound, SiHF 3 SiHCl, SiHBr, SiHI 3 



Boiling-point, —80° +33° about 110° about 220° 



— JBerichte, xxxviii, 52. h. l. w. 



2. Decomposition of Ammonium Sulphate by Hot Sulphuric 

 Acid in the Presence of Platinum. — It has been shown by Dele- 

 pfne that the use of platinum sponge for regulating the boiling 

 in the determination of nitrogen by Kjeldahl's method leads to a 

 large or even a total loss of the ammonia. This fact has been 

 confirmed by von Dam, who has shown that nitrogen gas escapes 

 during the operation. The subject has now been studied further 

 by Delepine, and the reaction has been satisfactorily explained 

 by him. It was found that metallic platinum dissolves in strong, 

 hot sulphuric acid, and that this solvent action does not depend 

 upon the presence of nitrous acid as has been supposed. It was 

 found also that in the presence of ammonium sulphate platinum 

 sponge does not lose weight appreciably when treated with the 

 hot acid, and it was shown that nitrogen gas and sulphur dioxide 



