MECHANICS A^D USEFUL ARTS. 71 



sulphate of iron is produced, containing 30 to 40 per cent sulphuric 

 acit I. The salt is decomposed by passing the vapor of ammonia from 

 the waste waters of the hydraulic mains through it. In this way 

 sulphate of ammonia and an oxide of iron are obtained. The oxide 

 of iron can be used again. The sulphate, of ammonia is purified by 

 crystallization. Mr. Cleland says that he has obtained 100 tuns of 

 sulphur in this way. 



rrt'i>'ii-<tft'ii of Sal Ammoniac. About two per cent of ammo- 

 nia 'id u - as water goes over with the tarry products and is collected at 

 the end of the hydraulic main in cisterns. This was formerly a waste 

 product; it is now saved, and the greater portion of sal ammoniac of 

 cv> .imierce is prepared from it. In London alone 840,000 tuns of 

 coal are consumed every year in the manufacture of gas. This yields 

 about ;>7, 000,000 Ibs. of gas water. The water is subjected to distilla- 

 tion in two retorts, the first of which is heated directly by the fire, and 

 the second by the latent heat of the steam from the first. The steam and 

 gas arc- passed through a worm to be condensed, and flow into a largo 

 leaden tank containing muriatic acid. Uncondensablc gases pass out 

 of the tank and are conducted through the fire where the sulphuretted 

 hydrogen is consumed, into the chimney. The muriatic acid is satu- 

 rated to neutrality, and requires very little further treatment for tho 

 formation of beautiful white crystals of sal ammoniac. This sal ammo- 

 niac is the starting-point in the manufacture of the salts of ammonia, 

 and can now be obtained in great abundance by the above method. 



Oil and Fat from Refuse oily Cotton, Waste, &c. Edward Tonybee 

 digests the refuse material in about half its weight of concentrated 

 sulphuric acid contained in leaden vessels and warmed by steam. 

 They are thus dissolved and the fat separated. After standing the 

 fatty acids collect on the top, and can be removed and further purified 

 by distillation. To the residual solution sufficient finely divided phos- 

 phate of lime is added to neutralize the sulphuric acid, and a valuable 

 compost containing phosphates and nitrogenous matter obtained. 



There is a great waste in our woolen manufactories of a valuable 

 substance ; that is, the oil of the wool. When wool has been thor- 

 oughly cleansed, it is found to have lost thirty, forty, or in some cases 

 as high as sixty percent of its weight, and the most of this is oil, an 

 excellent oil for some purposes, and especially for soap. There is an 

 establishment in England that takes wool to cleanse for the oil, mak- 

 ing no other charge for the work. 



The oil can be extracted by means of the bisulphide of carbon, 

 which is a cheap article. It is also used for extracting oil from the 

 r ipe seed instead of pressing the seed. It is also used for extracting 

 ih" alkaloids and the essential oils of plants. It has been stated that 

 it leaves no odor. 



NEW PLAN FOR UTILIZING SCRAP TIN. 



A new method of utilizing Scrap tin plate in the reduction of sulphur- 

 etted lead ore, has been devised by Prof. Everett of New York. The 

 theory of the reduction of sulphuretted lead ore by iron is based upon the 

 fact of the great affinity of iron at a high heat for sulphur. The metallic 

 lead is set free by the sulphur leaving the ore and uniting with the iron 

 forming the sulphide of iron. By the use of scrap tin plate the iron 



