1869.] Chemistry. 107 



auliydrous sulphate of protoxide of manganese are put into a two- 

 necked bottle, and then dissolved in twenty parts of warm water. 

 To this mixture is immediately added a solution of ten parts by 

 weight of tartrate of potash and soda (Kochelle salt), dissolved in 

 sixty parts of water ; the thorough mixing of the fluids is promoted 

 by well shaking the bottle ; after this there is added a quantity of 

 a solution of caustic potash sufficient to render the fluid quite clear ; 

 immediately after this the corks, perforated and fitted with very 

 tightly fitting glass tubes, are placed in the necks of the bottle, 

 which should be entirely filled with the mixed fluid just alluded to. 

 One of the glass tubes — the inlet tube for the gas to be tested — 

 should just dip a little under the upper level of the fluid ; the outlet 

 tube, on the other hand, should only reach halfway through the per- 

 foration of the cork, A very slow current of gas is now made to pass 

 through the fluid, and kej)t going for at least 15 minutes, and at most 

 one full hour. In case the gas is quite free from atmospheric air, 

 the fluid in the bottle will remain quite clear ; if even traces of air 

 are present, a faint coloration of the liquid will soon become appa- 

 rent ; with a larger proportion of air present in the gas the fluid 

 will soon be rendered, first light brown coloured, and afterwards 

 intensely black. Since these changes of colour are due to the oxida- 

 tion of the salt of manganese, it is evident that every care must be 

 taken to avoid the presence or access of accidental air; the fluid 

 in the bottle should reach the cork. It is best to cool the bottle 

 during the experiment with ice, if at hand, otherwise with very cold 

 water ; the current of gas must be slow. 



M. Monnier has discovered a process for refining sugar, which 

 is likely to prove of considerable commercial value. When a 

 current of anhydrous sulphurous acid is passed into a chamber 

 containing coarse sugar, a bleaching action ensues, and three-fourths 

 of the colouring matter of the sugar is destroyed, while no alteration 

 whatever is sufiered by the sugar itself. After this treatment, the 

 sugar is strongly impregnated with sulphurous acid, but the j)re- 

 sence of this body does not interfere with subsequent operations. 

 About four parts of sulphur are required for every 1000 of sugar, 

 but when the process is in regular operation, the amount of sulphur 

 can be sensibly diminished. The sulphurous acid gas is obtained 

 by bm'uing sulphur in a small furnace adjoining the chamber. 

 When the operation is terminated, the sugar is dissolved in water, 

 and the sulphurous acid neutrahzed by lime previously converted 

 into sucrate of lime. M. Monnier feared that, in practice, the 

 anhydrous sulphurous acid might modify the sugar, and convert a 

 portion into grape sugar. He has, however, convinced himself that 

 no action of this kind takes place ; the proportion of uncrystaUizablo 

 sugar, found by analysis, after treatment by the process, being 

 always exactly equal to the original amount. In all the experiments 



