Chemistry and Physics. 117 



selger, in distilling some samples of commercial bromine, found that 

 the boiling-point was not 122° F., but 248° R ; and that the color of 

 the liquid became gradually lighter, till it was eventually quite color- 

 less. On continuing the distillation to dryness, he obtained a residue 

 of charcoal. On separating the bromine from the last portions of the 

 distilled liquid by means of a solution of potash, an aromatic, oily, col- 

 orless liquid was obtained, which analysis proved to be carburet of bro- 

 mine ; this existed in various specimens of bromine to the extent of 6 

 or 8 per cent., and there is every reason to conclude that it was deri- 

 ved from the ether employed in the prepartion of this substance. 



20. Method of Soldering cast-iron with wrought-iron, (Technologiste ; 

 Lond. Jour, and Repert., vol. xxxiv, p. 280.) — The following process 

 has been recommended for this purpose : — First melt filings of soft cast- 

 iron with calcined borax in a crucible ; then pulverize the black vitre- 

 ous substance which is thereby produced, and sprinkle it over the parts 

 which are intended to be united ; after which, heat the pieces of cast 

 and wrought-iron and weld them together on an anvil, using only 

 gentle blows. This method is peculiarly applicable for the manufac- 

 ture of iron articles which are intended to be made red hot, and are re- 

 quired to be impervious to fluids or liquids ; as such a result cannot be 

 obtained by simple fastening. 



2i. Mode of Silvering Glass by the employment of Gun-Cotton, 

 (ibid.) — M. Vohl has recently discovered that a solution of gun-cotton 

 in a caustic ley, possesses, in a high degree, the property of precipita- 

 ting silver from its solutions in the metallic form. In fact, on bringing 

 gun-cotton into contact with a caustic ley of sufficient strength, the 

 cotton will become dissolved in the ley, giving out ammonia with a con- 

 siderable degree of heat, and producing a deep brown liquor, some- 

 what thick : on pouring an acid into this, a brisk effervescence is pro- 

 duced, carbonic acid and nitrous acid being disengaged. 



D CT 



ihm action of gun-cotton, in this instance, shews that it is not sim- 

 ply dissolved, but undergoes decomposition, by which the atoms of 

 oxygen, in the nitric acid, enter into combination with the atoms of car- 

 bon in the cotton, thus producing carbonic acid, which as well as the 

 nitrous acid produced by the nitric acid, combines with one part of pot- 

 ash. A fresh decomposition of nitrous salt by the potash, in presence 

 of hydrogenated substances, furnishes ammonia. 



The most remarkable property of this alkaline solution is the follow- 

 ing :— On pouring into it a few drops of a solution of nitrate of silver, and 

 adding ammonia until the oxyd of silver formed is re-dissolved (the 

 fixture being slowly heated in a water bath), the liquor will, at a 

 certain period, assume a deep brown color and effervesce, the whole 

 of the silver being precipitated on the sides of the vessel. The mir- 

 ror thus produced is much superior in brilliancy to those produced 

 by means of etherial oils or ammoniacal aldehyde; and the facility 

 *»th which it is produced will doubtless render it of practical im- 

 portance. 



This property is not exclusively possessed by gun-cotton ; it is found 

 a 'so in cane sugar, sugar of milk, manna, gums, and other substances 

 £hich may be rendered explosive by treating them with nitric acid. 

 p *cro.azotic acid produces, under the same circumstances, a reflective 



