2. By dissolving 180 grains of lead in nitric acid in a small thin capsule, and heating it till the salt was quite dry, I got 288 grains of salt, weighed in the capsule; 36 grains of this salt yielded 24¼ yellow oxide by a low red heat = 22½ lead. This gives 90 lead to 7 oxygen. 3d. Again, 36 grains of the above salt, dissolved in water, precipitated by ammonia, and well washed on a filter, gave 23+ grains of oxide separated from the filter, and this had acquired 1 grain, making 24+ grains of oxide from the 22½ lead as before; the residue of liquid gave no signs of lead by hydrosulphuret of ammonia. The same quantity of salt precipitated by an excess of lime water gave only 22 grains of oxide; but hydrosulphuret of ammonia precipitated 2+ grains of sulphuret of lead from the clear liquid. II. _Intermediate oxide or oxides._ Minium or red lead, &c. Minium is an article of commerce used as a pigment and for various other purposes. It is made by exposing the yellow or protoxide of lead finely pulverized to a low red heat in a current of air, and constantly stirring the oxide so as to expose fresh particles to the air. In two days the yellow oxide is converted into the red. Several authors observe that red lead usually contains 1, 2, or more grains per cent. of impurities insoluble in nitric and acetic acids; the specimen I used however was so pure as not to leave more than ⅓ of a grain per cent. of insoluble matter after being heated red and treated with dilute nitric acid. Some of the most remarkable properties of red lead are, 1st. It is never obtained in combination with any acid; 2d. It yields oxygen gas when exposed to a bright red heat or when treated with concentrated sulphuric acid, and is in both cases reduced to the protoxide; 3d. When treated with dilute nitric acid it is dissolved in part, but constantly leaves an insoluble brown residuum, which is the deutoxide, as will be shewn; the weight of the deutoxide obtained is by my experiments 20 per cent. and the part in solution is found to be the protoxide; 4th. When treated with muriatic acid, muriate of lead is formed and oxymuriatic acid given out; 5th. When treated with dilute acetic acid or cold concentrated acetic acid, ½ of the oxide is dissolved and the remainder is still red, its colour being rather improved; if concentrated acid be used and boiling heat applied, then ⅘ of the whole oxide is dissolved and ⅕ remains of brown oxide, the same as with nitric acid. Some of the above facts are new, and may contribute to elucidate this most curious oxide, which scarcely has a parallel. Proust is the only author I know who has given a plausible conjecture concerning the peculiar nature of this oxide. He supposes it a compound of the yellow and brown oxides. This I believe is the fact; but it will be found I apprehend to be a compound of 1 atom of oxygen with 6 of the yellow oxide, as will appear from what follows.