1CS ANNUAL OF SCIENTIFIC DISCOVERY. 



and passed through fine sieves. Including the portion which is 

 sieved out, and which, although it does not go into the oxidizer, 

 is usually charged to the process, the amount of lime used at 

 present averages 14 cwt. per ton of bleaching-powder prepared. 

 Until quite recently it was supposed that whatever proportion of 

 lime was used in the oxidizer, products could not be obtained con- 

 taining less than an equivalent of base (or bases) to every equiv- 

 alent of peroxide of manganese. Now, however, products are 

 regularly obtained containing only between 0.9 and 0.7 equivalent 

 of base, and there have been obtained, occasionally, compounds 

 containing as little as 0.5 equivalent of base ; in case of producing 

 regularly compounds containing only one-half an equivalent of 

 base, the amount of lime required for this purpose may be reduced 

 as low as 10 cwt. per ton of bleaching-powder, and already, at 

 one work on the T}*ne, the amount has been reduced to 12 cwt. 



The mechanical power expended in the injection of the neces- 

 sary amount of air into the oxidizer has hitherto averaged between 

 7 and 8 Gorge-power for 1 hour per 100 pounds MnO2 made ; but 

 this amount can probably be diminished. Expressed in terms 

 of the amount of bleaching-powder produced, it may be said that 

 the production of 1 ton of bleaching-powder requires the expendi- 

 ture of from 35 to 40 horse-power for 2 hours. 



The quantity of acid consumed per ton of bleaching-powder 

 made by means of mangauite mud, varies with the degree of care 

 with which the process is performed and with the general skill of the 

 manufacturer, being in some cases considerably below the average 

 quantity consumed in making a ton of bleaching-powder by means 

 of native manganese, while in other cases it is scarcely at all below 

 that quantity. To produce a ton of bleaching-powder by the ordi- 

 nary process there is required the amount of acid obtained from 

 not less than GO cwt. of salt, and often there is used as much acid 

 as would be produced from 80 cwt. of salt. By the new process 

 at least one manufacturer, whose mud contains as yet by no 

 means the minimum amount of base, consumes to the ton of 

 bleaching-powder only 170 cubic feet of acid at 24 Twaddell, a 

 quantity which may be produced by less than 48 cwt. of salt. 



The loss of manganese which occurs in this process at present 

 varies from about 4 per cent, to about 10 per cent. The deposit of 

 sulphate of calcium and other matters in the chloride of manganese 

 settlers has to be removed as a thin mud, that is, mixed with a 

 quantity of the solution of chloride of manganese. By suitable 

 washing the amount of manganese lost may be reduced to 2 per 

 cent., but it ordinarily averages 5 per cent. No other sources pf 

 loss exist, except it be from carelessness on the part of the work- 

 men. Beyond the sulphate of lime and other bodies which are 

 deposited in the chloride of manganese settlers, the only residual 

 product of the process, and the only other thing which has to be 

 thrown away, is the solution of chloride of calcium. As this- so- 

 lution represents all the lime and all the limestone used 

 in the process, and two-thirds of the chlorine contained in 

 the acid employed, attempts have been made still farther to im- 

 prove the process by the substitution of magnesia in the place of 



