TRANSACTIONS OF THE SECTIONS. 81 



equivalents of MnO, per equivalent of CaO, and the CaO in it was so feebly com- 

 bined that it readily decomposed chloride of manganese. The author's compound 

 contains only one equivalent of MnOj per equivalent of CaO, and has no action 

 upon salts of manganese. 



This compound has now been produced and reproduced to the extent of some 

 hundreds of tons. The process of producing it and applying it to the manufacture 

 of chlorine is conducted as follows : — The residual liquor which remains after a 

 charge of manganite has reacted upon hydrochloric acid in any suitable still is run 

 from the stiU into a well or other receptacle in which it is treated with carbonate 

 of lime, to neutralize any free acid, and to decompose any sesquichloride of iron or 

 sesquichloride of aluminium which may be contained in it. The neutralized 

 liquor is then pumped up into an elevated cistern, in which it is left at rest for a 

 few hours in order that it may deposit certain solid matters which it now holds in 

 suspension. The most abundant of these is usually sulphate of calcium, due to the 

 somewhat considerable quantity of sulphuric acid which is nearly always con- 

 tained in the hydrochloric acid produced in alkali works ; but there are also small 

 quantities of sesquioxide of iron, derived from the sesquichloride of iron in the 

 hydrochloric acid, and sometimes partly from the lime used in the process, and 

 larger or smaller quantities of alumina and silica, due to the lime. These im- 

 purities having deposited, the supernatant liquor, which is a mixed solution of 

 chloride of manganese and chloride of calcium, and is now quite clear and of a 

 beautifid rose coloiu', is run off into another vessel, where there is added to it the 

 quantity of lime necessarj^ to decompose the chloride of manganese in it and nearly 

 an equivalent more. A blast of air is then injected into the resulting mixture, and 

 what was at first a perfectly white mud, all the manganese in which was in the 

 state of MnO, soon becomes a very black mud, nearly all the manganese in which 

 is in the state of IMnO,. This is "then allowed to settle for about twelve hours, at 

 the end of which time it has separated into a denser black mud and a supernatant 

 clear solution of chloride of calcium. This solution of chloride of calcium having 

 been di-awn off, what remains is ready for use in the still. It is used as mud, 

 without drying, being conveyed to the still by pipes and entering by a hydraulic 

 lute. In the still it meets with hydrochloric acid, from which it liberates chlorine, 

 at the same time reproducing exactly such a residual solution as was commenced 

 with. With this solution the round of operation is recommenced ; and so on, over 

 and over again, continually. The samples exhibited were portions of a charge of 

 manganese which, at the works of Messrs. J. C. Gamble and Sons, of St. Helen's, 

 has actually generated chlorine, from which bleaching-powder has been made, 

 about fifty successive times. 



Hitherto the principal item in the cost of chlorine has been that for native 

 peroxide of manganese. Last year, in Great Britain, France, Belgium, and Ger- 

 many together, there were produced about 120,000 tons of bleaching-powder, 

 which cost, on an average, for native oxide of manganese, not much, if any, less 

 than £5 per ton. The author's process substitutes for this cost for native oxide of 

 manganese a cost for the regeneration of manganite of calciimi not exceeding 15s. 

 per ton of bleaching-powder, being about 10s. for lime, l.s. for steam. Is. for wages, 

 and 2s. for interest and wear and tear. Moreover, whereas hitherto, at least in this 

 country and in all but an extremely few exceptional cases, the production of a ton 

 of bleaching-powder has required the acid from about 75 cwt. of salt, this com- 

 pound yields chlorine enough for a ton of bleaching-powder from the acid from 

 less than 45 cwt. of salt. This larger yield of chlorine is mainly due to the arti- 

 ficial manganite being so easily soluble that it can very readily be caused to neu- 

 tralize from 95 to 99 per cent, "of the acid employed, which is a very much larger 

 proportion of it than can be neutralized when working with manganese ores. A 

 third very important advantage of the new process over the old one consists in this, 

 that whereas the immense quantities of acid which escape neutralization in the old 

 process are usually (and have almost necessarily to be) sent into the rivers, as 

 free acid, the only product of the new process which has to be thrown away is a 

 perfectly neutral solution of chloride of calcium. 



1869. 



