TIN-PLATES 1017 



One of the great items of expense in the manufacture of best iron, as before described, 

 is tho cost of charcoal for the fineries. About 1850 the attention of Mr. Rogers 

 was directed to the use of a substitute for charcoal in the finery. Careful thought and 

 experiment led him to the conclusion that some coals could be charred in such a way 

 as to produce a mechanical structure analogous to charcoal, and at the same time when 

 deprived of sulphur might be used in the finery. These experiments resulted in the 

 manufacture of ' charred coal.' This material has been worked at several of the prin- 

 cipal manufactories in South Wales, and declared equal in every respect to charcoal. 



The preparation of the ' charred coal ' is very simple. The coal is first reduced to 

 small, and washed by any of the ordinary means : it is then spread over the bottom 

 of a reverberatory furnace to a depth of about 4 inches ; the bottom of a furnace is 

 first raised to a red heat. When the small coal is thrown over the bottom a great 

 volume of gases is given off, and much ebullition takes place : this ends in the produc- 

 tion of a light spongy mass which is turned over in the furnace, and drawn in about 

 one hour and a half. To completely clear off the sulphur, water is now freely 

 sprinkled over the mass until all smell of the sulphuretted hydrogen gas produced 

 ceases. The result is 'charred coal.' The quantities of 'charred coal' hitherto 

 produced have been made on the floor of an ordinary coke oven, whilst red hot after 

 drawing the charge of coke. 



Tin Coating of Iron and Zinc, by Mr. Morries Stirling's patent process. For this 

 purpose the sheet, plate, or other form of iron, previously coated with zinc, either 

 by dipping or depositing from solutions of zinc, is taken ; and, after cleaning the 

 surface by washing in acid or otherwise, so as to remove any oxide or foreign matter 

 which would interfere with the perfect and equal adhesion of the more fusible metal 

 or alloy with which it is to be coated, it is dipped into melted tin, or any suitable alloy 

 thereof, in a perfectly fluid state, the surface of which is covered with any suitable 

 material, such as fatty or oily matters, or the chloride of tin, so as to keep the surface 

 of the metal free from oxidation ; and such dipping is to be conducted in a like 

 manner to the process of making tin-plate or of coating iron with zinc. When a fine 

 surface is required, the plates or sheets of iron coated with zinc may be passed be- 

 tween polished rolls (as already described) before and after, or either before or after 

 they are coated with tin or other alloy thereof. It is preferred in all cases to use for 

 the coating pure tin of the description known as ' grain tin.' 



Another part of the invention consists in covering, either wholly or in part, zinc 

 and its alloys with tin, and such of its alloys as are sufficiently fusible. To effect 

 this, the following is the process adopted : A sheet or plate of zinc (by preference 

 such as has been previously rolled, both on account of its ductility and smoothness) 

 is taken, and after cleaning its surface by hydrochloric or other acid, or otherwise, it 

 is dried, and then dipped or passed in any convenient manner through the melted tin, 

 or fusible alloy of tin. It is found desirable to heat the zinc, as nearly as may be, to 

 the temperature of the melted metal, previous to dipping it, and to conduct tho 

 clipping, or passing-through, as rapidly as is consistent with thorough coating of the 

 zinc, to prevent as much as possible the zinc becoming alloyed with the tin. It is 

 recommended also that the tin, or alloy of tin, should not be heated to a higher tem- 

 perature than is necessary for its proper fluidity. The metal thus coated, if in the 

 form of sheet, plate, or cake, can then be rolled down to the required thickness ; and 

 should the coating of tin or alloy be found insufficient or imperfect, the dipping is to 

 be repeated as above described, and the rolling also, if desired, either for smoothing 

 the surface or further reducing the thickness. 



Another part of the invention consists in coating lead or its alloys with tin or 

 alloys thereof. The process is to be conducted as before described for the coating of 

 zinc, and the surface of lead is to be perfectly clean. The lead may, like the zinc, 

 bo dipped more than once, either before or after being reduced in thickness by rolling. 



Lead and its alloys may also be coated with tin or its alloys of greater fusibility 

 than the lead to be coated. 



Crystallised Tin-plate. See MOIBEE METJLLLIQTJE. It would seem that the acid 

 merely lays bare the crystalline structure really present on every sheet, but marked 

 by a film of redundant tin. Though this showy article has become of late years viil- 

 garised by its cheapness, it is still interesting in the eyes of the practical chemist. 

 The English plates marked F, answer well for producing the Moirec, by the following 

 process : Place the tin-plate, slightly heated, over a tub of water, and rub its surface 

 with a sponge dipped in u liquor composed of four parts of aquafortis and two of 

 distilled water, holding one part of common salt or sal-ammoniac in solution. When- 

 ever the crystalline spangles seem to be thoroughly brought out, the plate must ba 

 immersed in water, washed either with a feather or a little cotton (taking care not to 

 rub off the film of tin that forms the feathering), forthwith dried with a low heat, and 

 coated with a lacquer-varnish, otherwise it loses its lustre in the air. If the whole 



