The Phosphates of America. 89 



duce 6199 litres of dry air in the case of brimstone and 8114.9 

 litres in the case of pyrites, each being calculated on the basis of 

 C. and a barometric pressure of 760 millimetres. These figures 

 serve to demonstrate that the quantity of sulphur to be profitably 

 burned per cubic foot of chamber space will fluctuate with the 

 higher or lower situation of the works. 



The ingenious differential anemometer invented by Pecles and 

 modified by Fletcher, and the beautiful and simple apparatus for 

 analyzing the chamber gases designed by Orsat, have so facilitated 

 the general process that an exactly proportioned current of air 

 may now be measured out to meet the varying requirements of 

 both situation and material employed. An example of this is 

 afforded by Buchner's careful analyses, which show that the 

 quantity of sulphurous-acid gas passed from the burners to the 

 chambers varies from six to eight per cent., according to the nature 

 of the pyrites, the construction of the furnace and the manage- 

 ment of the air-supply. His greatest average by careful working 

 was as follows : Sulphurous acid, 6.07 ; oxygen, 7.18 ; nitrogen, 

 86.74. The sulphurous acid requiring only 3.03 volumes of oxygen 

 for its transformation into H 2 SO 4 , it will be seen that after sub- 

 tracting this quantity from the above total there still remained 

 4.15 volumes to pass away with the nitrogen into the atmosphere, 

 and the greatest watchfulness should be invariably observed by 

 chamber managers to keep as nearly as possible within these 

 proportions. 



In some of the works where pyrites ores are burned, it is 

 still customary not to convey the hot gases from the burners 

 directly to the chambers, but to previously cool and at the same 

 time cleanse them from the dust by which they are generally ac- 

 companied by causing them to pass from the flues into an upright 

 brick stack, carried from an independent foundation to about 10 

 feet above the level of the furnace arch. From this they enter a 

 range of cast-iron pipes 2 feet 6 inches in diameter and 27 feet 

 long, in three lengths, cast in two halves, and each provided with 

 a man-hole to facilitate cleaning. 



These pipes are fitted into a tunnel of lead 5 feet square and 

 40 feet long, connected at its opposite extremity with the acid 

 chamber by a seven-pound sheet-lead pipe of about 1^- feet in 

 diameter. 



Intelligent and thoughtful managers have now discarded this 

 antiquated system in favor of a far simpler and more rational 



