ACETYLENE. 791 



ing to from fifty to seventy-five per cent of the original mass, 

 to fall throiigli into a bin, from which it is collected to be used 

 again. The lime requires to be fairly pure, over five per cent of 

 impurities interfering seriously with the production of carbide. 

 Magnesia is very undesirable, and it is stated that if over three 

 per cent is present a good quality of carbide can not be made. 

 This matter of impurities and the care of the carbon pencils, 

 which when properly looked after wear away only about 0"09 of 

 an inch per hour, but which may make a great deal of trouble if 

 carelessly tended, are the points requiring special attention. Un- 

 slaked lime is said to give the best results. The alternating cur- 

 rent is used at Spray, but a direct current can be employed. Be- 

 sides coke, soft coal, anthracite, charcoal, pitch, tar, resin, and 

 asphalt have been tried in combination with lime. Indeed, the 

 first mixture used by Mr. Wilson was lime and tar, which had 

 been boiled together in a caldron and then thoroughly dried. 

 With the exception of charcoal, however, none of these substances 

 were found of any value as compared with coke, although they 

 all produced some carbide. As regards the amount and quality 

 of the light obtained from acetylene properly burned, there seems 

 no question as to its great superiority over either ordinary coal 

 or water gas. It stands about even with water gas in poisonous 

 qualities, but is more liable to explosion. Greater care would be 

 required in handling it, especially if the proposition, which was 

 at first well received, to use it in a liquefied state from cylinders 

 under great pressure, should prove practicable. 



Its success as an illuminant, however, depends almost entirely 

 on the cost of manufacture, and regarding this point it is some- 

 what difficult at present to get reliable data, chiefly, perhaps, be- 

 cause of the experimental stage in which much of the apparatus 

 still is. 



The Progressive Age, a New York publication devoted to the 

 interests of electricity, gas, and water, recently formed a commis- 

 sion which it sent down to Spray for the purpose of determining 

 the actual cost of manufacturing calcium carbide. The commis- 

 sioners were Prof. Houston and Drs. Kennelly and Kinnicutt, and 

 their conclusions, after careful examination of the works and a 

 testing of two full runs, were published in the Progressive Age 

 for April 15th, and are as follows : 



" Our estimate, therefore, of the cost of producing calcium car- 

 bide at Spray, by working the furnaces three hundred and sixty- 

 five days a year and twenty-four hours a day, yielding on the 

 average one ton of two thousand pounds gross carbide a day, is 

 $32.76 per ton. Of this amount $14.39 is for material. The 

 freight charges on lime and coke are heavy at Spray, and add 

 materially to the cost." 



