SPONTANEOUS COMBUSTION OF METALS IN CHLORINE. 203 



antimony be sprinkled into a jar of cold chlorine (fig. 90) the anti- 

 mony particles will take fire and glow, combustion being brought 

 about on account of the absorp- 

 tion of the chlorine by the anti- 

 mony, and the production of 

 vigorous chemical action in 

 consequence ; thin leaves of 

 Dutch metal (a kind of brass) 

 will act in the same way. 



These experiments, however, 

 like all others involving the use 

 of chlorine gas, are not to be 

 recommended excepting in a room 

 where there are facilities for 

 freely ventilating and so carrying 

 off the chlorine which unavoid- 

 ably escapes into the air, other- 

 wise distressing coughing and 

 possibly serious injury to the lungs 

 may be brought about, owing to 

 the corrosive action of the gas 

 (Compare Expts. 162 and 180). 



Expt. 229. To Dissolve Gold. 

 Chlorine lias a powerful action 

 upon most metals tending to 

 combine with them producing 

 compounds termed chlorides; even gold is affected by this gas, 

 although most chemical agents have no action on this metal. If 

 gold leaf be placed in ajar of chlorine gas it will by and by disappear 

 becoming converted into chloride of gold, a compound easily soluble 

 in water, from the solution of which particles of metallic gold can be 

 precipitated by suitable agents (Expt. 135). Solution of chlorine 

 (Expt. 162) behaves in the same way; a few gold leaves placed 

 in a bottle which is then filled with chlorine water, will soon 

 disappear by becoming converted into chloride of gold and so dis- 

 solved. 



Expt. 230. To distinguish Gold from other Metals. Citric 

 acid has no action on gold ; thus gold leaf may be placed in a 

 wine glass and nitric acid poured over it without any of the metal 

 being dissolved; whilst a leaf of "Dutch gold" (an imitation 

 made of a variety of brass) would be instantly attacked and dis- 

 solved. If, however, some hydrochloric and nitric acids be 

 mixed together, gold will readily dissolve in the mixture, for 

 which reason the compound fluid has long been known as aqua 



Fig. 90. Antimony burning in 

 Chlorine. 



