352 EXPERIMENTS ON THE RELATION 



from the fire, and attend diligently to the application of the 

 ether. Dry muriatic acid gas, and common air, do not affect 

 iron in the cold, at least during a period equal to their joint 

 application in the present case, as I have found by experiment in a 

 graduated glass-tube over quicksilver ; and as the whole atmo- 

 spheric air was expelled, before the application of heat, the ef- 

 fect is solely due to the acid gas, as, indeed, its progressive in- 

 crease, with the duration of the process, sufficiently attest. 

 The oxygen of the atmosphere could have no influence on the 

 result *. 



There was found within the tube, near the end farthest from 

 the retort, on the verge of the ignited part, a white pulverulent 

 matter, glistening like snow, and the adjoining laminae of iron, 

 were encrusted with the same substance, in spangling crystal- 

 line plates. 



This powder dissolves readily in water. Into recently boil- 

 ed water, when a little of it was put, and a small fragment of 

 crystallised prussiate of potash was added, a greyish cloud ap- 

 peared, speedily becoming blue. Tincture of galls dropped 

 into a similar solution, gave the characteristic purple tin^e of 

 iron. Thirteen parts of it by weight, being ignited in a small 

 platina tray, evolved copiously a dark- brown smoke, smellino- 

 of muriatic acid, and left 6 parts, which were red oxide of iron. 

 But 13 of green muriate, by Dr Wollaston's scale, are equiva- 

 lent to 8 of red oxide. Does the above muriate contain the 



atomic 



* M. Gay Lussac, in his Recherches Physico-ch'nu'ques, describes a similar 

 experiment, but without the production of water. If the utmost precautions be 

 not taken, to keep the condensing tube at a very low temperature, the expanded 

 and heated acid gas will readily carry off the moisture, as I found in one experi- 

 ment. The neglect of these precautions will account for the difference of 

 M. Gay Lussac's result. 



