M. TECHNOLOGY. 537 



any way, to heat from a stove, a furnace, or any other form 

 of heating. 



As tlie result of the same e^vj^eriraents. Professor Attfield 

 concludes that, although mineral oils are especially liable to 

 combustion, in consequenco of their vaporization, yet they 

 never act as those of animal and vegetable origin do, when 

 applied to fibrous or other substances, in producing sponta- 

 neous combustion. 14 A, March 22, 1873, 745. 



ZINCING IRON. 



The following is an excellent and cheap method for protect- 

 ing iron articles exposed to the atmosphere, such as cramp- 

 irons for stone, etc., from rust ; They are to be first cleansed 

 by placing them in open wooden vessels, in water, contain- 

 ing three quarters to one per cent, of common sulphuric 

 acid, and allowed to remain in it until the surface appears 

 clean, or may be rendered so by scouring with a rag and wet 

 sand. According to the amount of acid, this may require 

 from six to twenty-four hours. Fresh acid must be added 

 according to the extent of use and of the liquid, and when 

 this is saturated with sulphate of iron, it must be renewed. 

 After removal from this bath, the articles are rinsed in fresh 

 water, and scoured until they acquire a clean metallic sur- 

 face, and then kept in water in which a little slaked lime has 

 been stirred until the next operation. When thus freed from 

 rust they are to be coated with a thin film of zinc, while cold, 

 by means of chloride of zinc, which may be made by filling a 

 glazed earthen vessel, of about two to three gallons' capacity, 

 three fourths full of muriatic acid, and adding zinc clippings 

 until eftervescence ceases. The liquid is then to be turned 

 off from the undissolved zinc, and preserved in glass vessels. 

 For use, it is poured into a sheet-zinc vessel, of suitable size 

 and shape for the objects, and about one thirtieth per cent, 

 of its weight of finely powdered sal ammoniac added. The 

 articles are then immersed in it, a scum of fine bubbles form- 

 ing on the surface, in from one to two minutes, indicative of 

 the completion of the opej*ation. The articles are next drain- 

 ed, so that the excess may flow back into the vessel. The 

 iron articles thus coated with a fine film of zinc are placed 

 on clean sheet-iron, heated from beneath, and perfectly dried, 

 and then dipped, piece by piece, by means of tongs, into very 



