448 M. Kraut on a Lecture Experiment. 



is replaced by cadmium, the fusing-point is not altered. An 

 alloy of 50 parts of solder (PbSn 3 ) and 50 parts Bi is liquid at 

 92-93°. The author has further determined the fusing-point of 

 the following alloys : — 



Specific gravity. 



1 Cd 

 Cd 



Cd 2 



6Pb 7Bi , 

 Bi 2 Pb 3 , 

 Bi 4 Pb? 



, *- > 



Found. Calculated. 

 . 10-529 10-330 

 , 10-563 10-275 

 . 10732 10-341 



Differ- 

 ence. 



0199 

 0-288 

 0-391 



Fusing- 

 point. 



o 



88 



85-5 



95 



The first alloy was prepared according to the proportions given 

 by Wood, who found 82° as its melting-point. The others are 

 prepared in equivalent proportions. 



According to a statement of Troost*, a magnesium wire of 

 97 millims. in length and 33 millim. in thickness, gives by its 

 combustion as much light as sixty-four candles ; and this inten- 

 sity is increased to 110 when the combustion takes place in 

 oxygen. He also mentions that an equally intense and more 

 economical light is obtained if, instead of pure magnesium, an 

 alloy of magnesium and zinc is burned. 



Kraut describes the following lecture experiment f. A pla- 

 tinum wire 0-5 millim. in thickness is coiled fifteen to twenty times 

 round a lead pencil so as to form a spiral, the end of which is 

 passed through and round a longish cork crosswise. This spiral 

 is hung in a wide-necked flask of about 450 cubic centiins. capa- 

 city, standing on wire gauze over a lamp : ammonia- water of 

 20 per cent, is poured in this flask so that the point of the 

 spiral just stands above the liquid. On the other hand, a gas- 

 holder of oxygen is connected with a bent glass tube (20 millims. 

 in the clear) the end of which just dips in the liquid. If the 

 spiral is now heated to redness, and oxygen is allowed to enter, 

 the flask at first fills with wirite vapours of nitrite of ammonia, and 

 then with intense red ones of nitrous acid; and in general the 

 glass tube which conveys the oxygen is covered with a crust of 

 nitrite of ammonia. If now the ammonia-water is warmed, the 

 mixture of oxygen and ammonia-vapour explodes with a loud but 

 perfectly safe explosion, by which the platinum wire is cooled 

 down below the temperature at which it visibly glows. In a few 

 moments the spiral is heated to redness, the gas mixture is again 

 exploded, and so on ; thus the experiment can be repeated as often 

 as is liked. With a rapid current of oxygen it burns for some 

 time under the liquid; and if the end of the tube is placed 



* Cosmos, 1865, p. 533. 



f Liebig's Annalen, October 1865. 



