MECHANICS AND USEFUL ARTS. 113 



India-rubber is dissolved, he adds ammonia, of a strength of 30 

 per cent., in the proportion of about equal parts by weight of 

 ammonia to the India-rubber contained in the solution ; when the 

 mass has become of a grayish-white color it is ready to be mixed 

 with the pulp. 



A protective coating for iron and other metals has been in- 

 vented by Mr. J. Crouziers, of Ollioules, France, to which the 

 inventor has given the name of Electro-Catlwdic Insulating Mastic, 

 which to the scientific reader will convey the fact that its 

 application will prevent the corrosion of metal when immersed 

 in fluids calculated to generate galvanic action. Its composition 

 and application are as follows : Take of sulphur (say) 38 per 

 cent. ; coal tar, 20 per cent. ; gutta-percha, 5 per cent. ; minium, 

 or red lead, 6 per cent. ; white lead, 7 per cent. ; pitch, 10 per 

 cent. ; resin, 10 per cent. ; spirit of turpentine, 4 per cent. ; total, 

 100. Melt the sulphur in one vessel, and coal tar, gutta-percha, 

 minium, white lead, pitch, and resin, all together, in another; 

 but before adding the gutta-percha to the coal tar, dissolve it, as 

 far as possible, in the spirit of turpentine, and when all these 

 ingredients have melted, pour in the sulphur very gently from the 

 separate vessel, then thoroughly mix the whole, and apply the 

 composition hot by the aid of a brush, by dipping the article to be 

 coated into it, or in any convenient manner. 



Mr. Crockford, of Dublin, Ireland, has invented several new 

 processes for utilization of waste products. One of these is a 

 method of treating what is known as flux skimmings, produced 

 in the process of galvanizing or coating iron with zinc. For this 

 purpose he adds a sufficient quantity of hydrochloric or sulphuric 

 acid to the flux skimmings to dissolve all the zinc, and then pre- 

 cipitates all the zinc with the ammoniacal gas arising from the 

 distillation of gas liquor, by which means he obtains oxide and 

 sulphide of zinc and hydrochlorate or sulphate of ammonia. 

 Sometimes he passes through the solution, toward the end of the 

 operation, a stream of sulphuretted hydrogen, for the purpose of 

 rendering the precipitation quite complete. 



A second process by the same inventor consists in the treat- 

 ment of the liquor from paper mills resulting from boiling esparto 

 grass, wood, or other materials in caustic soda. He first evapo- 

 rates the liquor to diyness, and then submits the dry product to 

 distillation at a red heat, whereby the volatile and other matters 

 are collected, and he afterwards extracts the carbonate of soda 

 left in the furnace or retort in which the distillation has been 

 effected by lixiviation, at the same time extracting a quantity of 

 black, similar to " lamp-black." 



The same inventor has devised a method of condensing and 

 collecting the fumes and gases from the flues of furnaces in which' 

 lead and other ores are smelted. To do this he draws off the 

 mixed fames and gases from the flues of furnaces wherein lead 

 or other metal is smelted, and forces them, by means of a fan or 

 other similar means, into and through a quantity of filtering 

 material, such as canvas, cotton, or fine coke, which material 

 may be renewed from time to time whe-u it becomes clogged : be- 



