SODIUM CHLORIDE BERTHOLLETS LAAVS 



443 



obtained from all other 

 metallic chlorides. 33 ' It is 



53 Thus the metallic chlorides, 

 which an- decompo^-d toa._ 

 or lessdegree by water^ornespond 

 with feeble bas-s. Such are, for 

 example, MgCL, A1C1.-, SbCl-, 

 Bid.-. The decomposition of 

 magnesium chloride (and also 

 carnallite) by sulphuric acid pro- 

 ceeds at the ordinary temperature 

 and inaij l>' i-injilui/ct? as a con- 

 venient incihoil far t/t>' ^roilnc- 

 tion qf hydrochloric acid. The 

 vapour of common salt in the pre- 

 sence of steam and silica (which 

 is capable of combining with so- 

 dium oxide) gives hydrochloric 

 acid and sodium silicate. Hydro- 

 chloric acid is also produced in 

 many reactions of decomposition 

 of carbon compounds containing 

 chlorine and hydrogen; for in- 

 -tance, when the vapour of ethyl 

 chloride is passed through a red- 

 hot tube, it gives defiant gas and 

 hydrochloric acid. It is also pro- 

 duced by the ignition of certain 

 metallic chlorides in a stream 

 of hydrogen, especially of those 

 metals which are easily reduced 

 and difficultly oxidised for in- 

 stance, silver chloride. Lead 

 chloride, when heated to redness 

 in a stream of steam, gives hy- 

 drochloric acid and lead oxide. 

 In general 2MC1 + nH->O fre- 

 quently gives MoO ; , + 2, ( HC1, and 

 MCLj+H,, sometimes M-f/tHCl, 

 although both these reactions 

 also proceed in the opposite di- 

 rection, that is, M..O,, + ?i2HCl fre- 

 quently forms 2MCl n + nU..,O and 

 sometimes M + HC1 = MCI,, + 

 H n , where 31 is a metal. The 

 multitude of the cases of forma- 

 tion of hydrochloric acid are un- 

 derstood from the fact that it is 

 a substance which is compara- 

 tively very stable, resembling 

 water in this respect, and even 

 most probably more stable than 

 water, because, at a high tem- 

 perature and even under the 

 action of light, chlorine decom- 



FIG. 66. Coke tower. 



