and the Black Oxide of Iron at a wJdte heat. 247 



tity whatever gases are evolved. A stoppered bottomless jar of the 

 ordinary construction for the iron-wire experiment, and of 291 

 cubic inches' capacity, was made use of in the following trials. 

 Eighteen experiments were made with it, and from 100 to 110 

 grains of fused globules were obtained from each combustion. A 

 test-tube, with a funnel fixed into it by a perforated cork, and filled 

 with water, was arranged so as to receive the gas. In some expe- 

 riments it was placed within the oxygen jar, so that the coil of wire 

 when introduced hung close to it, a piece of tin plate being arranged 

 so as to guide the globules within the edge of the inverted funnel* 

 In the greater number of trials, however, the tube and funnel were 

 placed outside of the vessel containing the oxygen, and an inclined 

 plane of tin plate was so sloped as to carry the globules past the 

 edge of the jar, and within the mouth of the funnel. No difference 

 of result was observed in experiments made in both ways, but the 

 latter arrangement was preferred as more convenient, and as enabling 

 more oxygen to be employed at each trial. 



In all the experiments, permanent gas was evolved when the 

 fused globules fell into the water. This statement is to be consi- 

 dered as applying ta each combustion considered as a whole ; for in- 

 dividual globules were frequently observed to give off* no gas at all, 

 or to evolve so very little, that it might be air separating from the 

 water, in which it had previously existed in solution. The quantity 

 of gas obtained at each combustion varied greatly. Sometimes as 

 much as a cubic inch was procured, more frequently only half that 

 quantity, and occasionally less. The globules from thick coils of 

 wire gave off a larger volume of gas than those from thin ones. 



Portions of the gas were transferred to a Grove's eudiometer over 

 water, and exposed to a white-hot platinum wire. They did not 

 kindle or detonate, nor were they sensibly diminished in volume 

 Other portions were subjected to electric sparks and discharges in a 

 syphon eudiometer over water, with the same negative results ; but 

 when air or oxygen was mingled with the gas, it exploded sharply 

 with heated platinum or the electric spark. When a match was ap- 

 plied to the open end of a tube containing the unmingled gas, it 

 burned rapidly with a pale blue flame, but did not explode. The 

 gas given off during the action of the fused globules on water, was 

 not, then, a mixture of oxygen and hydrogen. 



Its freedom from all but a trace of oxygen was ascertained in 

 other ways. To one portion of the gas standing over water nitric 

 oxide was added, but no ruddy fume or yellow coloration shewed 

 itself. When phosphorus was introduced into the gas, in one in- 

 stance it did not smoke, but in the greater number of cases it fumed 

 for a brief period, and occasioned an amount of contraction barely 

 perceptible. The gas appeared to be nearly pure hydrogen. To 

 ascertain if it certainly were so, a portion of it was carefully dried, 

 by chloride of calcium, and transferred to a eudiometer over warm 



