Feb. 1, 1865.] THE TECHNOLOGIST. 



TIN AND ITS USES. 331 



that it was these deposits in ancient times, and not the lodes, which gave 

 such interest to this country, enduring yet in the word of Britain, or 

 Etain, the Tin-land. Thus far the ore received in this country from 

 Australia partakes of these characteristics, leaving in all probability 

 large lodes to be worked and explored when, as in Cornwall, the deposits 

 become insufficient to satisfy the demand. As time advances, however, 

 we shall doubtless notice this distinction — viz., instead of the system of 

 smelting by the use of a blast furnace, a reverberatory will be used, 

 and, probably, discoveries in chemistry will be made which will render 

 the mode of reduction yet more satisfactory and philosophical. 



The description of ore now under notice being found in a granulated 

 state, or in the form of small grains, the operation of stamping is unne- 

 cessary, and from its being free from sulphur, and altogether purer than 

 the kinds previously spoken of, it is adapted for different purposes from 

 those already named. 



There is a difference between tin plate and best grain. The former 

 not being quite pure, containing a little iron, is used in some of its many 

 modifications, for coating the superior kind of tin plates ; and the latter, 

 requiring great care and circumspection in selection, is used, when 

 smelted, by the dyers as mordants. When a piece of cloth is to be 

 dyed, it is absolutely necessary to preserve its texture, and fix the dye, 

 whatever it may be, in neutralising its destructive elements by a solu- 

 tion of tin in acid, and hence the term mordant, a killing of the in- 

 jurious constituents of the dye. For this purpose it is necessary the tin 

 should be pure, because, if impure, the solution would render the dye 

 and the cloth dull and dirty. When smelted, an interesting operation is 

 performed in preparing it for use, called " granulating," which is done 

 by the immersion of a hot block, weighing about four hundredweight, 

 in a vessel of liquid tin, and after a short space of about twenty minutes, 

 just at the moment of melting, it is lifted out and struck gently, and in 

 this condition the crystals will separate, the block being fractured into 

 a thousand pieces, which adapts it for solution by presenting so many 

 surfaces for the action of the acid. 



Having considered the mineral, its preparation, and adaptability, the 

 process of assaying comes next, so as to discover the product of metal 

 in any given quantity ; and this is accomplished at the smelting-house, 

 or place of purchase. The system generally adopted is that of weighing 

 a portion or sample of the ore, about two-and-a-half ounces, representing 

 20 parts — or 100 parts, at the option of the assayer, — then adding to this 

 4-5ths of culm, or anthracite coal, as a flux, with l-20th of fluor spar ; 

 ' the whole having been mixed together, is put into an assay furnace, in 

 a crucible, and in about fifteen or twenty minutes the operation of 

 smelting is performed by the oxygen of the mineral entering into com- 

 bination with the carbon from the culm, eliminated by heat during com- 

 bustion ; a rapid boiling action takes place, but after awhile ceases, the 

 cessation of this action demonstrating that the whole of the oxygen has 



