70 Rev. J. E. Ashby [March 23, 



purposes. Coal-gas mixed with air may also be employed under 

 the gauze upon which the oxide is distributed. Euchrome (dug 

 from the estate .^of Lord Audley) is a cheap and useful catalyzing 

 agent, when freed from its carbon.* A mixture of ten parts by 

 weight of chlorate of potash, with one part of light and finely 

 divided sesquioxide of iron, yields oxygen with entireness and 

 facility, and has the additional advantage that {n) grains of the 

 mixture represent very nearly {n) cubic inches of evolved oxygen. 

 If we take the case of the sesquioxide of iron, we are able, to some 

 extent, to show the modus operandi of the catalytic action ; we can 

 arrest the process at the half-stage, and then at leisure complete the 

 other half. By heating Feg O3 to redness, and quenching it in 

 boiling alcohol (air being excluded), or by passing the vapour of 

 alcohol over heated sesquioxide, we obtain two results ; the alcohol 

 is oxidated, and the Fcg O3 becomes Fcg O4 by deoxidation. The 

 same follows by treating the sesquioxide with ammonia, gaseous or 

 in strong solution. This black magnetic oxide (probably Fcg O4 

 + H O) remains unchanged by a red heat, if oxygen be not present ; 

 but if warmed in contact with air, it absorbs oxygen at a temperature 

 far below redness, and returns into the original Fcg O3. It is clear, 

 then, that during the catalysis, an intestine motion of the particles 

 is going forward, and every portion of the sesquioxide is constantly 

 reduced by the alcohol and reoxidated from the air. This was il- 

 lustrated by a diagram and a cluster of coloured balls. Attention was 

 then drawn to a singular fact, which may probably be referable 

 to the catalytic action of the sesquioxide of iron. If the ferro- 

 cyanide of barium be heated until it ceases to give off ammonia, 

 and then placed over alcohol, ammonia is again evolved in small 

 quantity ; but if the same experiment be tried with pure prussian 

 blue, a large quantity of ammonia is formed by the contact with 

 alcoholic vapour. Alumina (AI2 O3) presents a singular pheno- 

 menon, hitherto unobserved ; a pure specimen, of snowy whiteness, 

 on being heated to redness, and exposed to the vapour of alcohol, 

 becomes dark-grey, or black, and the vapour is oxidated ; and this 

 effect may be produced (with less ease) by ammonia. It seems 

 that the sesquioxide of alumina has become a lower oxide, as in 

 the case of iron, but cannot recover oxygen from contact with 

 that gas. 



INIr. Ashby then exhibited a " galvanic indicator,'* by which he 

 hopes to prove satisfactorily, whether or not a galvanic current is 

 set in motion during catalytic combustion. In conclusion, he drew 

 attention to several points of interest connected with catalysis. 



* Mr. Arthur Church has observed that several of the chromates (copper, 

 manganese, cobalt, &c.) after ignition, will freely catalyze alcoholic and other 

 vapours. 



