4 PEOCEEDINGS OF THE AMERICAN ACADEMY 



During these experiments the volume of the solution was gradually 

 increased by tlie hydrochloric acid used in washing as above described, 

 so that at last the volume amounted to 100 cubic centimetres. 



It will be noticed that the amount of oxidation increased with the 

 time of exposure, and that, so long as the amount was small, it was 

 as nearly proportional to the time as could be expected under the 

 varying conditions. The increased activity shown by determination 

 No. 5 appeared to be due to the intensely warm weather and bright 

 sunshine during the period, and the last determination would seem to 

 indicate that, after the oxidation reached a certain limit, the process 

 went on more slowly, as we should naturally expect; but, with the 

 greatly vai-ying conditions during this long period, no certain conclu- 

 sion can be drawn in regard to the effect of any single cause. 



The action we are discussing is entirely in harmony with the chem- 

 ical relations of antimony. The most striking characteristic of this 

 elementary substance is its tendency to form compounds of the radical 

 antimonyl, SbO. The oxichlorides, the oxibromides, and the oxi- 

 iodides, whose relations we have discussed so fully in our previous 

 papers, are examples in point, and we have been continually surj^rised 

 by the appearance of such compounds in reactions in the most unex- 

 pected ways. In this respect antimony closely resembles vanadium, 

 and with this element antimony is more closely allied than with its 

 familiar associate, arsenic. What the precise reaction is in the present 

 case we are not prepared to state. That it is not the simple conver- 

 sion of a terchloride into a pentachloride we are convinced ; but, in 

 order to elucidate the subject, further investigations are necessary. 



In this connection we may appropriately add that while the above 

 determinations were in progress we repeated the experiment described 

 on page 19 of our previous paper (loc. cit.). We treated in an open 

 flask 5 grammes of finely powdered pure metallic antimony with 50 cu- 

 bic centimetres of strong and pure hydrochloric acid, to which we added 

 only one cubic centimetre of the very dilute nitric acid (5.4 per cent) 

 described above. The flask was placed in a warm, protected place 

 (30° C), and shaken from time to time. Soon the acid became col- 

 ored reddish-yellow, and the chemical action began. When it had 

 apparently ceased, the contents of the flask were shaken together, and 

 the solution became at once as colorless as water ; but, on standing in 

 the air, the color rapidly returned, spreading from the surface of the 

 liquid downward. These phenomena were repeated again and again 

 during four or five months, imtil the whole of the metal dissolved. 

 According to the reaction usually assumed to take place under these 



