BETWEEN MURIATIC ACID AND CHLORINE. 333 



forward, in order to bring a little of the salt within the sphere 

 cf the heat. Great nicety was required in the advancement of 

 the sealed extremity ; for the glass tube being perfectly soften- 

 ed in its middle, too sudden volatilisation of the salt never 

 failed, by inflating and bursting it, to spoil the experiment. 

 This accident frequently happened. On the other hand, if the 

 central part of the tube was exposed to merely a dull red, the 

 experiment would not succeed with silver and copper. At 

 this temperature they did not decompose the sal ammoniac. 

 When, however, the above-mentioned precautions were obser- 

 ved, dew could be perceived to settle speedily on the cool por- 

 tion of the tube. This dew became more and more visible as 

 the sublimation advanced, till, finally collecting into distinct 

 drops, it trickled down the sides in striae, and formed a fila- 

 ment along the bottom. To obtain good results of this kind, 

 four or five hours must be devoted to one experiment, in 

 which 20 grains of salt, and from 60 to 100 of metal, are em- 

 ployed. More rapid transmission of the salts effects mere sub- 

 limation. Bubbles of gas come over, which, with silver and 

 copper laminae, are found to be a mixture of ammonia and hy- 

 drogen. In this case, the liquid condensed, is water of ammo- 

 nia. 



The metallic laminae are evidently heavier than before their 

 introduction ; but the increase of their weight could not be ex- 

 actly ascertained, because a portion of the silver or copper is 

 impressed on the inner surface of the tube, giving it a very 

 beautiful iridescent and metallic lustre, similar to the colours 

 of the diamond beetle, viewed in a microscope. The silver la- 

 minae, have for the most part exchanged their native brilliant 

 white, for a dull-brown or greyish hue ; and instead of being 

 eminently tough and ductile, have become more brittle than 

 any substance with which I am acquainted. The slightest 



touch 



