WATER. 



balls of the size of peas, and dried, at first slowly, and afterwards 

 more rapidly, the balls will act in the same manner as the sponge, 

 and their power is renewed by heating them in the blowpipe flame ; 

 being thus treated, they will, if preserved from dust, answer a 

 thousand times, and more ; their size need not be over 2, 4, or 6 

 grains. If one of the balls, fastened for convenience, to a piece of 

 platinum wire, be introduced into a mixture of air 100, and hydro- 

 gen gas 50 measures, it will in a few minutes be reduced to 87 ; the 

 diminution, 63, divided by 3=21, the proportion of oxygen. 



(jf.) In general, the platinum at common temperatures does not 

 act upon the gases that are found mixed with hydrogen ; but if the 

 ball is hot, it sometimes acts upon the residuary nitrogen to form 

 ammonia, and produces a diminution greater than 63. 



(g.) Moist platinum sponge has the same power as dry, only it re- 

 quires a longer time. If some of the ammonio-muriate of plati- 

 num be ignited in the sealed end of a glass tube, or if its solution be 

 decomposed there, by a rod of zinc, a thin film of the metal will ad- 

 here firmly to the interior of the tube. In such a tube, a mixture of 

 oxygen and hydrogen, or of the latter and common air, will be de- 

 composed in a few hours : and if the hydrogen prevail, all the oxy- 

 gen will disappear ; in this manner hydrogen can be perfectly puri- 

 fied from oxygen ; even one part in 100 will be abstracted, which much 

 exceeds the power of hydrogen alone, aided by the electric spark. 



(A.) Dobereiner supposed this to be a peculiar galvanic arrange- 

 ment, in which the hydrogen represents the zinc, and the platinum 

 the copper ; but it appears that no heat is produced, unless oxygen 

 or atmospheric air is present ; so that the office of the metal appears 

 to be to produce a combustion of the hydrogen. 



(i.) Platinum, in fine powder, produces no action, not even a slow 

 one ; the laminated metal and its wire are equally inert, but thicker 

 leaves and wire acted, although slowly, when heated to between 

 200 and 300, Centigrade. A very thin film of platinum, rolled 

 round a glass tube, or suspended freely in a detonating mixture, pro- 

 duced no effect in several days ; but when crumpled like the wad- 

 ding of a gun, it produced instant detonation. 



(j.) Platinum sponge strongly ignited, loses the property of becom- 

 ing incandescent ; but produces slowly, and almost imperceptibly, the 

 combination of the two gases. 



(k.) This phenomenon appears still more remarkable, when it is 

 considered that it happens between the lightest and the heaviest body 

 known. 



(L) If, upon a mixture of spongy platinum, and nitrate of platinum, 

 and ammonia, a jet of hydrogen be directed, the mixture reddens, 

 crackles, and emits inflamed sparks. 



