CHLORINE.

137

Which, while less than an equivalent, was such that the batch could not haveconsisted entirely of acid manganites, in which the peroxide remaining afterdeduction of the quantity equivalent to the combined lime contained in thebatch was in any other proportion to the basic manganese contained in thebatch than either that of two equivalents to one or that of three equivalentsto two—a fact almost irresistibly suggestive of the two bodies being combined.The circumstance, moreover, that under no known conditions can peroxide ofmanganese be formed, by treating protoxide with air in the wet way, withoutsome portion either of manganese itself or of some other metal going simul-taneously into combination as base, strongly indicates that only salts ofmanganous acid can be formed in that way.

“ The quantity of air which requires to be blown into the oxidiser per givenquantity of peroxide of manganese made varies with a considerable number ofconditions, but more especially with the depth of the charge operated upon,and with the quantity of manganese contained in a given volume of it.Within all practicable limits, increase of the depth of the column blown into isequivalent to increase of the quantity of air blown ; and the more particles ofprotoxide are contained in a given volume of the charge, the larger is the totalsurface which they present for the air to act upon, and the greater is the pro-portion of the total oxygen injected which becomes absorbed. The proportionof the oxygen absorbed to the quantity blown in being of course greatest atthe commencement of the operation and afterwards continually diminishing, atime at length arriving, if the blowing be continued long enough, at which nomore oxygen is absorbed at all, the proportion of the total quantity of oxygenabsorbed to the total quantity blown in is also considerably influenced by hownearly to that point the operation be continued. As an illustration of whatis obtained on the large scale, it may be stated that a certain batch contained1987 pounds of peroxide, reckoned as Mn 0 2 , which was made in four hours,by the injection of about 240,000 cubic feet of air, being at the rate of about120 cubic feet of air for every pound of Mn 0 2 made.

“ The quantity of acid consumed per ton of bleaching-powder made bymeans of manganite mud varies with the degree of care with which the processis performed and with the general skill of the manufacturer, being in somecases very considerably below the average quantity consumed in making a tonof bleaching-powder by means of native manganese, while in other cases it isscarcely at all below that quantity. I believe that a ton of bleaching-powderis never made in this country, by means of native manganese, from less thanthe acid from 60 cwts. of salt, and only rarely from less than the acid frombetween 70 and 80 cwts. of salt. At least one manufacturer, however, whosemud contains, as yet, by no means a minimum of base, and who at presentfollows a method of treating the mud in the stills which is not quite the mosteconomical of acid, is consuming, per ton of bleaching-powder made by meansof manganite mud, only 170 cubic feet of acid at 24 0 Twaddell—a quantitywhich I believe to be producible, in practice, from less than 48 cwts. of salt.As what one manufacturer is doing can surely be done by all, when equallyfamiliar with the process, I venture to believe that a very considerableeconomy of acid will eventually be realised by the process everywhere.

“ The loss of manganese which occurs in the process at present varies fromabout 4 per cent to about 10 per cent. The only unavoidable source of loss