4)28 Dr. Schafhaeutl on the Different Species of 



The contents of the test glass poured on a filter were care- 

 fully washed with ammonia, and the liquid afterwards evaporated 

 to dryness in a platinum crucible. This dry remainder was 

 perfectly white ; only in the corner of the crucible some brown 

 matter was collected, in all probability a species of humine. 

 This dry residuum weighed 0'3 grains, was after ignition 

 perfectly white, and had lost 0*08 grains. It dissolved in 

 hydrochloric acid, left silica behind, which I was unable to 

 weigh, and carbonate of ammonia threw down alumina mixed 

 with some silica. 



In consequence of this, 5*53 grains would have contained 

 aluminum equal to 0*298793 grains. To account for 0"0188 

 hydrogen we ought to have 0'44<0893 aluminum. By actual 

 analysis I found 0*352583; but it might very well have hap- 

 pened that, in separating alumina from phosphoric acid, a 

 part remained combined with the acid. 



The gray residuum which had been treated with ammonia, 

 dried and weighed, was 1 *82, and had therefore lost 0*28 grains, 

 that is to say 0*02 grains less than the weight of alumina ob- 

 tained. This extraordinary evolution of hydrogen takes 

 place with all residuums of hotand cold-blast gray iron, but 

 with the former more than the latter; and perfectly white iron 

 never evolves any gas whatever; yet white iron which is 

 nearly approaching to gray iron gives always traces of hy- 

 drogen. 



What causes this extraoi'dinary decomposition of water? 

 We know no other chemical body which, left as a residuum 

 after being treated with acids, possesses the power of decom- 

 posing water by the presence of ammonia, except aluminum ; 

 and as the ammonia had really dissolved alumina, which only 

 occurs when it comes in contact with the metallic base of alu- 

 mina, we may safely conclude, that the exti'aordinary evolu- 

 tion of hydrogen was here produced by the presence of me- 

 tallic aluminum. 



Solution of caustic potash ley likewise decomposes the gray 

 residuums, but only at a higher degree of temperature, and 

 then a species of slight explosion takes place and the fluid is 

 thrown with some violence out of the crucible. 



Viewed through a microscope, the residuum of this gray cast 

 iron appears to be composed of white gelatinous transparent 

 nodules, which generally surround a centre, consisting of some 

 dull black spots and of a scale, sometimes shining like graphite, 

 but of a more silvery whiteness. The mixture of these scales 

 with the white nodules gives the powder, to the naked eye, the 

 appearance of having a grayish colour ; these scales remain 

 after being treated with ammonia, though not at all apparently 



