312 Royal Society :— Dr. J. W. Mallet on the Gases 



The final experiment was made as follows, with great care, and 

 with all precautions which could be thought of to avoid error. 



A parallelopiped of iron was cut upon a planing-machine from 

 the largest of the three masses found (that spoken of as No. 1* in 

 the paper above referred to), the work being done with special care, 

 to avoid the least trace of grease being derived from the machine. 



Not only was the cutting-tool itself made red-hot in the blacksmith's 

 fire, hardened in clean water, and tempered and ground without con- 

 tact with any thing greasy, but every part of the machine-bed, set- 

 screws, and frame, from which any risk was to be feared, was care- 

 fully cleansed, and paper used to cover the whole of the iron, except 

 where actually borne upon by. the tool. The piece of iron measured 

 about 75 millims. long, 16 millims. wide, and 12 millims. thick. It 

 was cut from as solid a portion of the mass as could be found, 

 and was quite bright upon the surface and free from crust, though 

 traces of a very minute crack or fissure were barely perceptible at 

 one end. The piece weighed 124*589 grammes ; and as the specific 

 gravity of the iron had been found to be 7'853, the volume was 

 15"87 cub. centims. A new and perfectly clean porcelain tube, with 

 sound glaze, was used, heated by a small upright fire-clay furnace 

 with good draught, through holes in the opposite sides of which the 

 tube was passed. The fuel was charcoal, in pieces a little larger 

 than a walnut. The Sprengel pump had a fall-tube of about 1 '34 

 metre long ; its connexions were made with great care, and were 

 protected by outer casings of india-rubber tube, with the annular 

 space between the tubes filled with glycerine. A plate of glass float- 

 ing on the mercury in the funnel at top served to prevent the risk 

 of air being carried down, as the metal was gently poured on through 

 another and smaller funnel with narrow aperture. 



A good vacuum having been obtained in the cold, lighted charcoal 

 was placed in the furnace, and gas very soon began to come. off. 



It was determined to analyze separately that collected at the be- 

 ginning, middle, and end of the process, in order to see whether the 

 different constituent gases were given off at the same or at different 

 rates. The total amount obtained was 36*33 cub. centims., reduced 

 to 0° C, and 1 metre pressure. This was divided into three portions 



* The results of ordinary analysis were: — 



Iron 88-706 



Kickel 10-163 



Cobalt -396 



Copper -003 



Tin -002 



Manganese trace. 



Phosphorus -341 



Sulphur -019 



Chlorine -003 



Carbon -172 



Silica , -067 



99-872 



