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Show APPENDIX F.- CHEMICAL ANALYSIS. 421 the crystals was heated to drive off the water of crystallization.. Having previously learned that it was an alum, with the double base of manganese and alumina, I made a careful analysis and obtained the following result from the salt dried by blotting paper:- % 100 grammes of the freshly crystallised salt gave- Water „ 78.0 Protoxide of manganese. 08.9 Alumina. .' : .• , 04.0 .- Bnlphorio acid..,. ,...; .....^ 18.0 Iff is not easy to explain the relation of the acid to the two bases here in accordance wjth the usual constitution of alums, as there does not Beem to be enough acid for the supply of an equivalent to each base, nor of alumina for the manganese. But as I have not the. time to repeat my experiments, they must stand for what they are worth. This salt may be substituted for common alum in nearly all its various uses for- tanning, in combination with the salt brine of the Great Salt Lake, in what is called the process of tawing; and where. tan bark is difficult to obtain, it is a valuable acquisition to the arts. And should the locality of alum at any time give out , from exhaustion, the rock may be blasted and the alum made by • artificial means, as the alum slates of England are worked. The manganese alum is also susceptible of various uses as a mordant and a colouring agent in dyeing,' where it is not only a substitute for common alum, but subserves other and additional purposes of communicating various tints of fancy colours to shades of red, browp, fcc. Thus we have purples, lilacs, brpwns, and many other tints, from the use of manganese, For details in this art, see ParnelTs Applied Chemistry- rCalico-printing.. YOUTB truly, L. D. GALB. HOWARD STANSBUBY, ESQ. r Captain Corps of Topographical Engineer*, U. S. Army, WASHINGTON, March 25,1851. |
