NEW PROCESS OF ELECTRO-PLATING. 465 



ill the air. We have already referred to this action in an article on " Irides- 

 cence in Glass," which appeared in the Journal for April, 1877. According 

 to Griffiths, a fiint-glass bottle in which a solution of carbonate of animonia 

 had been kept for a long time was so much acted upon by the liquid that 

 flakes of glass could be detached by shaking it. 



All acids also act upon glass, especially if there is an excess of alkali in 

 its composition, or, as already intimated, if it contains lead. Wine and 

 other acid liquids kept in bottles have often been found contaminated with 

 salts, resulting from the solution of the metals in the glass. Wine is some- 

 times put into bottles made of glass wholly unfit for the purpose, and its 

 taste and color are affected in a very few days by the salts produced by cor- 

 rosion. We can imagine that serious mischief might occasionally arise 

 from putting up domestic wines, fruit juices, and the like in bottles not in- 

 tended for any such use. 



The rapid and intense action of hydrofluoric acid upon glass is due to 

 its remarkable affinity for silica, which it separates at once from the vitre- 

 ous salt, forming a fluoride of silicon. As many of our readers are aware, 

 advantage is taken of this chemical reaction in the process of etching glass. 

 The surface to be etched is coated with wax, and the lines to be engraved 

 cut tlirough Avith a pointed instrument. The glass is then exposed to the 

 fumes of hydrofluoric acid, produced by the action of sulphuric acid on 

 powdered fluor spar (fluoride of calcium), and is corroded where the wax 

 has been removed. The experiment is one that requires special caution on 

 account of the highly poisonous character of the acid vapor. 



These are but a few out of the many facts connected with the chemistry 

 ot glass, but the length to which the article has extended forbids us to pur- 

 sue the subject further at present. — Boston Journal of Chemistry. 



NEW PROCESS FOR ELECTRO-PLATING. 



Professor A. W. Wright, of Yale College, New Haven, Conn., has discov- 

 ered a new and brilliant method of electro-plating, which promises to be of 

 great utility. Taking advantage of the fact that the various metals may be vol- 

 atilized by the electrical current, he provides a hollow vessel, from which the 

 air is partially exhausted ; within this vessel he arranges opposite to each 

 other the two poles of an induction coil ; the article to be electro-plated, a 

 bit of glass for example, is suspended between the poles; to the negative 

 pole is attached a small piece of the metal that is to be deposited on the 

 glass. From l^ree to six pint Grove cells are employed, yielding, by means 

 of the induction coil, an electrical spark from two to three inches in length. 

 Under the influence of this spark a portion of the metal of the electrode is 

 converted into gas or volatilized, and condenses upon thie cooler surface of 

 the suspended glass, forming a most brilliant and uniform deposit. The 

 thickness of the plating thus produced may be regulated at will,, by simply 



