VOL. LXXXVI.] PHILOSOPHICAL TRANSACTIONS. 5 



sulphuric acid, left a residuum of lead and siliceous earth *. Two drs. of the 

 purified ore were mixed with an equal quantity of pot-ash, and afterwards exposed 

 to the fire in a crucible. The mixture melted without intumescence. When cold, 

 the mass was of a reddish colour, and the surface was covered with small scales. 

 Water was poured on it, and the solution was saturated with nitric acid. The 

 next day, the bottom of the glass was found covered with projecting crystals, about 

 -£• of an inch in length : these crystals were formed of small glittering rhomboi- 

 dal plates, heaped one on the other. Their flavour was rather metallic. They 

 quickly melted with the blow-pipe, on charcoal, without any increase of bulk, and 

 became small* round drops, which were immediately absorbed by the charcoal. 

 When melted by the blow-pipe in a silver spoon, ,the,y appeared as small grains, 

 of a greyish colour, which became streaked in cooling, and deposited a white pow- 

 der during the operation. 



When the phosphate of ammonia and soda was melted, and some of these 

 crystals were added, they speedily dissolved, and communicated to the salt a green 

 colour, more or less deep according to the quantity employed. They completely 

 dissolved in distilled water, when heated. Prussiate of pot-ash with this solution 

 produced a reddish-brown precipitate, not very dark. When some drops of muri- 

 atic acid were mixed with the solution of these crystals in water, and a small piece 

 of tin was added, the liquor became of a deep blue. The solution of muriat of 

 tin poured on the crystals produced the same effect. 



Mr. Klaproth from these experiments concludes, that the crystals are the aci- 

 dulous molybdate of pot-ash, especially as the crystals obtained from the filtrated 

 solution of the molybdaena of Altenberg, detonated with nitre, and saturated with 

 nitric acid, have the same properties. As in the above experiment the ore did 

 not appear to have been completely decomposed, Mr. Klaproth mixed 2 drs. of the 

 purified ore with 10 of carbonate of pot-ash, melted the whole in a crucible, and 

 reduced it to powder, and dissolved it in water. The solution was filtrated, par- 

 tially saturated with muriatic acid, and heated. A white precipitate fell, resembling 

 curdled milk, which consisted of molybdic acid, and a still larger quantity of 

 oxyde of lead. When dissolved in muriatic acid, the lead was precipitated in the 

 state of muriate of lead. This precipitate being separated by a filter from the 

 alkaline solution partially saturated with muriatic acid, the solution was then com- 

 pletely saturated with the same acid, and again became slightly turbid, and depo- 

 sited a white precipitate, which resembled starch in cold water. This precipitate, 

 after it had been washed and dried, was subjected to the same experiments as the 

 above-mentioned crystals, and exhibited the same properties, excepting that it did 

 not dissolve in distilled water till some drops of muriatic acid were added. 



When the solution was evaporated in a glass basin, the rest of the oxyde of 

 molybdaena was deposited in the form of a heavy citron-coloured powder. The 

 white oxyde of lead on the filter through which the solution of the alkaline mass 

 * Analyse Chimique du Plomb Spathique jaune de Carinthie An. de Chiraie, 1751, p. 103.— Orig. 



