1869.] Chemistry. 105 



very small ; this is easily understood, as the substance does not 

 leave the retort, but undergoes all the processes within it. 



Professor Stas gives the following as the best method of pre- 

 paring sulphurous acid, a gas which is largely used as a reducing 

 agent and disinfectant. A cm-rent of sulphurous acid is obtained 

 by attacking, by means of copper, pm'e sulphuric acid, diluted with 

 from one-half to two-fifths its volume of water. To make sure of 

 the purity of the sulphurous acid, pass the current, at first through 

 water contained in a large washing flask, then through two Woulfe's 

 bottles completely filled with pumice-stone broken into small frag- 

 ments and moistened. The moistened pumice-stone, previous to 

 its introduction into the bottles, is twice calcined with sulphuric 

 acid, so as to free it from the chlorides and fluorides which it often 

 contains. 



Professor Wohler, to whom we owe the first published account 

 of aluminium and magnesium, has lately published the foUowiug 

 facts concerning the metal cerium. The colour of the metal is 

 intermediate between the colour of iron and that of lead. The 

 metal is lustrous when polished ; it is malleable. Its density is 

 about 5 "5 at 12^. Exposed to the air it loses its lustre, and 

 becomes slightly blue. It feebly decomposes water at 100°. 

 Hydrochloric acid dissolves it with energy; concentrated nitric 

 acid converts it into clear brown oxide ; the dilute acid dissolves 

 it. By evaporation, a white salt is obtained, which leaves, after 

 calcination, a brown oxide, insoluble in nitric acid and in dilute 

 sulphuric acid. Concentrated sulphuric acid slowly dissolves this 

 oxide, forming a yellow solution which shows the reactions of eerie 

 salts. Hydrochloric acid dissolves this oxide with disengagement of 

 chlorine, forming a colourless solution. When a globule of cerium 

 is heated by the blow-pipe to dull redness, the metal inflames and 

 burns vividly, forming brown oxide ; but upon submitting a globule 

 suddenly to a very high temperature, it bm-ns with explosion, 

 sending out bluish sparks. Cerium powder can inflame below 

 100'. 



The rapid and accurate estimation of the amount of sulphur 

 contained in pyrites is a matter of importance to that very large 

 section of industrial chemists who are interested in the manufactm-e 

 of vitriol. Professor Wohler has discovered that hypochlorous acid 

 may be used to transform the sulj)hur of pyrites into sulphuric 

 acid, which is then estimated by baryta. He dfrects to finely 

 pulverize the mineral and suspend it in water, through which a 

 current of gaseous hypochlorous acid, or better still hypochloric 

 acid, is passed ; this entirely dissolves the pyrites. Hypochlorous 

 acid is prepared by heatmg a milk of carbonate of Imie, thi'ough 

 which a current of chlorine is passed to saturation. Hypochloric 



