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M. TECHNOLOGY. 59 1 



dred and eighty grains of sulphocyanide of potassium, forty- 

 five grains of chloride of gold, and one quart of water, slight- 

 ly acidified with hydrochloric acid. It should be slightly 

 warmed. The deposit of gold immediately formed answers 

 the purpose of producing the bluish tint with sulphide of am- 

 monium. A heavier film can be obtained by this bath with 

 a galvanic current. U (7, 1873, CCVIII.,47. 



MANGAXESE A SUBSTITUTE FOR XICKEL IX THE ARTS. 



In view of the present high price of nickel. Dr. Percy, the 

 eminent metallurgist, proposes to substitute manganese for 

 it in the preparation of German silver, and maintains that 

 it is impossible for the most experienced manipulator to de- 

 termine the difference, except chemically. A further article 

 on this subject in the Chemical News^ indicates the best meth- 

 od of obtaining manganese sufliciently pure for the purpose, 

 as also for refining it ; and it is here suggested that there is 

 nothing to prevent pure metal being obtained in large quan- 

 tity, and at a comparatively low price. 1 A^May 23, 1873, 

 249. 



CASTING METAL IX A VACUUM. 



In order to avoid the difliculties and defects occasioned by 

 the air inclosed in moulds in casting, especially with works 

 of art. Cumin and Martel have devised the plan of producing 

 a vacuum in the mould, at the instant of casting, by connect- 

 ing it with an air-pump, which removes the air. The inte- 

 rior is faced with a sufiiciently porous and refractory mate- 

 rial, varying with the nature of the metal to be cast ; dried 

 plaster-mortar answering for such as are readily fusible, such 

 as type-metal ; plaster-mortar, mixed with graphite, alum, or 

 other materials, well ground together and thoroughly dried, 

 for the less fusible, such as bronze ; and graphite alone for 

 the most refractory, such as iron and steel. 5 C, 1873, 119. 



UXIOX OF IROX AXD STEEL. 



For many purposes it is frequently desirable to unite iron 

 and steel, the advantages of such a combination beinsr verv 

 great. There are, however, a number of difliculties in the 

 way of accomplishing this result. With edge-tools, for ex- 

 ample, the tedious hand labor required makes the j^roduct 



