DYEING AND CALICO PRINTING.

manganous acid upon protoxides of other metals. For example, as I statedbefore, whereas if protoxide of manganese by itself be treated with air inthe wet way, only one-half of it undergoes peroxidation, the other half beingapparently required to furnish base to the half which becomes peroxidised, ifa mixture of protoxide of manganese and an equivalent of lime be treatedwith air in the wet way, the whole of the protoxide undergoes peroxidation,and the lime ceases to be capable of either reading on chloride of manganeseor of dissolving in solution of chloride of calcium. Similarly, if protoxide ofmanganese, suspended in solution of either baryta, strontia, soda, or potash,be treated with air, baryta, strontia, soda, or potash goes out of solution, andthere is formed an insoluble compound containing one equivalent of man-ganese, three equivalents of oxygen, and one equivalent of barium, strontium,sodium, or potassium, as the case may be.

“ With the existence and modes of formation of normal manganites of allthese metals we were formerly acquainted ; what is new is the apparentformation, under the conditions of working on the large scale at which wehave arrived recently, of acid manganites, or double manganites of metal andhydrogen. By far the greater number of batches containing less than anequivalent of base which have been made as yet resemble in constitution oneor the other of the two representative batches. In one of the batches of the totalmanganese operated upon 86’5 per cent had been peroxidised, and for eachequivalent of peroxidised manganese present there were 0’85 equivalent ofbases. Regarding the constituents of the batch, for convenience, as Mn 0 2 ,MnO, and CaO, and considering the total manganese present as a thousandequivalents, there were thus in this batch 865 equivalents of Mn 0 2 , 135equivalents of MnO, and 0-85 times 865, or 735 equivalents of total bases,135 of which were MnO, the remaining 600 being CaO. Assuming that the600 CaO were combined with 600 Mn 0 2 , as normal manganite of calcium,there remained 265 equivalents Mn 0 2 and 135 equivalents of MnO, the pro-portion of the former to that of the latter being very nearly two to one.These figures I hold to show the existence in this batch of an acid manganite,MnH 2 (Mn03) 2 , or a compound containing the elements of one of normalmanganite of manganese and one of manganite of hydrogen. In the otherbatch, of the total manganese present 8i'5 per cent had been peroxidised, andfor each equivalent of peroxide present there were 0'885 equivalent of bases.This batch, therefore, contained 815 equivalents of Mn 0 2 , 185 equivalents ofMnO, and 536 equivalents of CaO. Assuming, as before, that all the limeexisted as CaMn 0 3 , there were left 2jg Mn 0 2 and 185 MnO. This is almostexadtly three of the former to two of the latter, suggesting the existence inthat batch of a sesquimanganite of manganese, containing the elements oftwo of normal manganite of manganese with those of one of manganite ofhydrogen. In these batches it is only acid manganites of manganese that Isuppose to have existed ; but one or two batches have been made, containingnot much more than 0'5 equivalent of base, in which I believe that theremust also have been an acid manganite of calcium. It may be, of course,that in all batches containing less than an equivalent of base a portion of themanganous acid exists in the free state; but I have not yet met with anyinstance of a batch, the blowing of which I have known to have been con-tinued until peroxidation had really ceased, and the proportion of base in