CHEMISTRY. 



181 



be used for common gilding. By stamping 

 and grinding the foil, in the manner in which 

 the ordinary powders are produced from tin 

 and brass, the new bronze powders are obtained. 

 The foil and the powders are applied by press- 

 ing or dusting them upon varnished surfaces. 



Paints from Iron Slag. The iron slag pro- 

 duced in puddling furnaces, containing a large 

 quantity of oxide, can, it is found, when re- 

 duced to powder, be employed as a substitute 

 for litharge, as a drier for paints. It is pre- 

 pared by pulverizing, washing and drying. It 

 serves not only as a cheap drier for paints, but 

 also when mixed by itself with oil, as a cheap 

 paint for coarse uses. 



Silvering Cloth. Mr. J. Cimeg, of London, 

 has patented a process for depositing metallic 

 particles upon fabrics of silk or wool. He 

 states that the concentrated juice of fruits, as 

 of currants and apples, contains in small 

 amount a chemical principle capable of acting 

 as a mordant on cloth, and of precipitating 

 from the state of solution the particles of 

 certain metals, as silver and gold. Having 

 cleansed thoroughly a silk or woollen fabric, 

 to remove from it all oily and gummy matters, 

 he immerses it (for silvering) for a short period 

 in a solution of nitrate of silver, ammonia, and 

 Rochelle salt ; after this the fabric is steeped 

 in the fruit juice. In consequence of the reac- 

 tion then taking place, pure silver is, from the 

 solution of the nitrate previously taken up by 

 the cloth, deposited upon its fibres. The fab- 

 ric being cleansed in soft water, the silver is 

 found to adhere to it, and so as to be incapable 

 of removal by washing. 



Rendering Fabrics Non-inflammable. In a 

 notice of this subject in the CYCLOPAEDIA for 

 1862, mention was made of the use for the pur- 

 pose specified of the chloride of zinc, the sul- 

 phate of ammonia, tungstate of soda, and com- 

 mon salt. It is recommended also to mix the 

 phosphate of ammonia with chlorhydrate of 

 the same base ; an efficacious solution should 

 contain 20 per cent, of this mixture ; or of the 

 sulphate alone a 7 per cent, solution will prove 

 equally effectual. Either of these can be ap- 

 plied in those manufactures where stuffs are 

 stiffened under the action of hot air or by cyl- 

 inders heated by steam; but they cannot be 

 xised where the common smoothing-iron is to 

 be employed, from the fact of their being then 

 decomposed by the heat. In such case, how- 

 ever, a 20 per cent, solution of tungstate of 

 soda may be employed; but like borax, alum, 

 &c., this is liable to destroy the thread of cot- 

 ton stuffs. All these solutions should be ap- 

 plied to the stuffs after they have been first 

 stiffened with starch and dried. Common salt 

 is not liable to either of the sorts of objection 

 holding against the ammonia salts on one hand, 

 and the tungstate of soda on the other. 



M. Sauvageon has discovered that cotton 

 stuffs exposed for awhile to the vapor of burn- 

 ing sulphur, assume snch a degree of incom- 

 bustibility that, although they will char and 



become brittle when held over the flame of a 

 spirit lamp, yet they cannot be made to take 

 fire ; while in the same circumstances, similar 

 fabrics not so prepared are inflamed at once. 

 It would appear an easy matter to subject 

 white clothing after washing to the vapor of 

 sulphur ; and an incidental effect would be that 

 of bleaching it more perfectly. How often the 

 exposure would be necessary appears not yet 

 to be known ; nor, perhaps, whether the fibre 

 is damaged in consequence. But the suffocat- 

 ing and poisonous properties of the sulphur 

 vapor (sulphurous acid) would evidently neces- 

 sitate much precaution in any attempts at a 

 domestic application of this method. 



Caustic Soap for Cleaning Flax, &c. In 

 the "Scientific American" to the weekly no- 

 tices of discoveries and of important patents ap- 

 pearing in which, we are indebted also for some 



other items under this topic date of April 



4th, 1863, an account is given of Mr. Henry's 

 patent for a highly caustic soap, to be used in 

 the treatment of flax, hemp, nettles, straw, 

 grass, &c., to obtain fibre for spinning. The 

 soap is made by combining a concentrated 

 solution of caustic alkali with oil, grease, or 

 other saponifiable substance, in such a way as 

 to secure an excess of alkali. Mr. Henry states 

 that after the gathering of flax, &c., no further 

 preparation than that of steeping in a solution 

 of such soap is requisite : the fibre will then 

 be properly freed from the glutinous matters 

 of the plant ; and pulp for paper may also be 

 thus obtained. The use of the soap in moder- 

 ate quantity is said to take the place of the 

 usual rotting process, and to render the subse- 

 quent crushing operation much more easy. 

 The gummy and oily parts of the plant are so 

 removed, or disintegrated, that upon subsequent 

 washing a clean and beautiful fibre is obtained. 



Purification, and also Concentration, of 

 Waters, by Freezing. Sea-water, in freezing, 

 forms flakes of ice consisting of nearly pure 

 water, the residual liquid being then extremely 

 saline, so that in some northern countries it is 

 used to furnish salt. Dr. Robinet, of Paris, 

 has recently applied the same process for the 

 purification of fresh water. He found the ice 

 of water taken from the Seine, and from wells 

 and springs, and then frozen, to be nearly as per- 

 fectly freed from such impurities as salts of lime 

 and magnesia, as is distilled water. It is accord- 

 ingly now proposed to procure fresh water on 

 shipboard, not by distillation, but by congelation. 



Again, the concentration of mineral waters 

 has long presented a difficult problem, from 

 the fact that, if heat were resorted to, it ex- 

 pelled the gases in solution in such waters. 

 Dr. Henry, of Paris, has now experimented by 

 congelation upon forty varieties of mineral 

 water, reducing these to \, yV, and even J fl of 

 their original volume, but without removing or 

 altering the gases contained in them. It is 

 quite certain, however, that in some cases 

 changes will under such process take place in 

 the salts in solution ; and so far, this will vary 



