on various Objects, 21 



ganesc, made red hot in a glazed porcelain tube, the bore of 

 which was nearly an inch in diameter; in this case a so- 

 lution of nitrous acid, sufficiently strong to be disagreeably 

 sour to the taste, and which readily dissolved copper, was 

 formed. 



This experiment was repeated several times, and, when 

 the diameter of the tube was large, with precisely the same 

 results. When red oxide of lead was used instead of oxide 

 of manganese, no acid was however generated; but upon 

 this sub nance a single trial only was made, and that in a 

 small tube, so that no conclusion can with propriety be 

 drawn from this failure. 



1 stated in the last Bakerian lecture, that in attempting 

 to produce ammonia from a mixture of charcoal and pearl- 

 ash, that had been ignited by the action of water, in the 

 manner stated by Dr. Woodhouse, 1 tailed in the trial in 

 which the mixture was cooled in contact with hvdrogen. 

 I have since made a number of similar experiments. In 

 general, when the mixture had not been exposed to air, 

 there was little or no indication of the production of the 

 volatile alkali ; but the result was not so constant as to be 

 entirely satisfactory; and the same circumstances could 

 not be uniformly obtained in this simple form of the ex- 

 periment. I had an apparatus made, in which the pheno- 

 mena of the process could be more rigorously examined. 

 Pure potash and charcoal, in the proportion of one to four 

 in weight, were ignited in the middle of a tube of iron, 

 furnished with a system of stopcocks, and connected with 

 a pneumatic apparatus, in such a manner that the mixture 

 could be cooled in contact with the gas produced during 

 the operation ; and that water exhausted of air could be 

 made to act upon the cooled mixture, and afterwards di- 

 stilled from it : figures of this apparatus, and an account 

 of the manner in which it was used, are annexed to this 

 paper. In this place I shall state merely the general re- 

 sults of the operations, which were carried on for nearly 

 two months, a variety of precautions being used to prevent 

 the interference of nitrogen from the atmosphere. 



In all cases in which the water was brought in contact 

 with the mixture of charcoal and potash, when it was per- 

 fectly cool, and afterwards distilled from it by a low heat, 

 it was found to hold in solution small quantities of am- 

 monia ; when the operation was repeated upon the same 

 mixture, ignited a second time, the proportion diminished ; 

 in a third operation it was sensible, but in the fourth barely 

 perceptible. The same mixture, however, by the addition 



B3 of 



