VOL. LXXXVI.] PHILOSOPHICAL TRANSACTIONS. > ig 



The decomposition of the nitrate of ammonia is also well known ; and I have 

 no doubt but that muriate of ammonia suffers a similar decomposition in a 

 smaller degree each time that it is sublimed; for whenever I have had occasion to 

 sublime muriate of ammonia, I have always found some fuming muriatic acid; 

 and from whence could this be produced, but from a portion of the salt which 

 was decomposed during the sublimation. The distillation of the triple salt, com- 

 posed of molybdic acid, muriatic acid, and ammonia (§ 7 and 9,) places this in 

 a stronger light ; for whenever this salt was distilled, a certain portion of molybdaena 

 was left in the retort deprived of oxygen, and muriatic acid was found in the re- 

 ceiver. Moreover, from several repetitions of this experiment, I am well con- 

 vinced, that by a great number of sublimations the whole of the molybdaena might 

 have been obtained in the proportion that the muriate of ammonia was de- 

 composed. 



When all these facts are considered, it appears more than probable that most, if 

 not all, of the ammoniacal salts suffer different degrees of decomposition whenever 

 they are treated in the dry way. As the molybdic acid was my principal object, I 

 did not make all the experiments I could have wished on this neutral salt; neither 

 have I as yet exactly determined the proportion of azotic gas produced from a 

 certain quantity. I have found however, that the sublimed undecomposed part of 

 the salt amounted to 183 grs. when an ounce of the salt had been distilled, and 

 that the liquid in the receiver weighed 145 grs.; so that 152 grs. had escaped, 

 which principally consisted of azotic gas, together with some sulphureous acid, 

 and some alkaline gas, which had made their way out of the vessels during the 

 operation. 



Continuation of the experiments on the molybdate of lead.— From the effects 

 which I observed to be produced when sulphate of ammonia was distilled with 

 molybdic acid, I was induced to examine in a similar manner the blue solution b : 

 but first I collected, washed, and dried the pale yellow precipitate which had been 

 formed when the sulphuric solution of the molybdic acid was saturated with ammo- 

 nia*. This precipitate, when dry, appeared of a deeper yellow, and easily dis- 

 solved in muriatic acid. Prussiate of pot-ash was then added to the clear solution, 

 which precipitated the whole of the dissolved matter in the state of Prussian blue. 

 The filtrated solution b was now evaporated till it became a dry concrete salt, the 

 colour of which was pale greyish blue. I collected this salt, and having reduced it 

 to powder, put it into a small glass retort, and having fitted on a receiver, I distilled 

 it in the same manner as was employed with the sulphate of ammonia. The pro- 

 ducts which came over were also the same; and when the bottom of the retort 

 began to be softened by the heat, I removed it, and found the residuum to be a 



* Whenever the solution was sufficiently diluted, I always found that ammonia precipitated the iron 

 free from any part of the molybdic acid 5 but when either of the fixed alkalies were used, a portion of 

 molybdic acid was precipitated with the iron into a state similar to the first portions of those white floc- 

 eulent precipitates, which have been already mentioned in § 9 and 10. — Orig. 



D 2 



