Part 12 (1/2)

This calx turns blue by exposure to light; and an hundred grains of it heated with charcoal will yield sixty grains of a peculiar metal, in small particles, which, when broken, look like steel It is soluble in the vitriolic or marine acids, and reduced to a yellow calx by nitrous acid or aqua regia

_Of Molybdena_

Molybdena is a substance which o; but its texture is scaly, and not easily pulverized, on account of a degree of flexibility which its laminae possess With extreme heat, and mixed with charcoal, it yields srey, brittle, and extre with several of the metals, it forms with them brittle or friable compounds By heat it is converted into a white calx

_Of Solid Combustible Substances_

There yet remains a class of solid substances, of the _combustible_ kind, but most of them have been already considered under the forinally formed, as _bituredients of which they are coo_

There only remains to be mentioned the _diamond_, which is of a nature quite different froredient in which is siliceous earth, which renders them not liable to be much affected by heat On the contrary, the diaree of heat soreater than that which will ht flame, diminishes common air, and leaves a soot behind Also, if diamond powder be triturated with vitriolic acid, it turns it black, which is another proof of its containing phlogiston

The diamond is valued on account of its extreme hardness, the exquisite polish it is capable of, and its extraordinary refractive power; for light falling on its interior surface with an angle of incidence greater than 24 will be wholly reflected, whereas in glass it requires an angle of 41 degrees

LECTURE XXIX

_Of the Doctrine of Phlogiston and the Coreat discovery of Mr Stahl, that all inflammable substances, as well as ave the naiston, and that the addition or deprivation of this substance es in bodies, especially that the union of a metallic calx and this substance makes a iston from the substances that contain it That it is the same principle, or substance, that enters into all infla disengaged fro into the coiston of charcoal or inflaiston of any of the metals, when the calx is heated in contact with either of them

On the contrary, Mr Lavoisier and most of the French chemists, are of opinion, that there is no such principle, or substance, as phlogiston; that metals and other inflammable bodies are simple substances, which have an affinity to pure air; and that co from the inflammable substance, but in the union of pure air with it

They moreover say, that water is not, as has been commonly supposed, a simple substance, but that it consists of two eleene_, and another, to which they give the naene_, which, with the principle of _heat_, called by them _calorique_, is inflammable air

The principal fact adduced by the when they beco, is, that mercury beco pure air, and that it beco with it

This is acknowledged: but it is al revived without the help of soistic substance; and in this particular case it is not absurd to suppose, that theprecipitate per se, iston, as well as i with that air In many other cases the saiston, as cast iron, malleable iron, and steel Also there is a calx of mercury made by the acid of vitriol, which cannot be revived without the help of inflaiston: and that the inflammable air is really imbibed in these processes, is evident, fro left in the vessel in which the process is made beside the metal that is revived by it If precipitate per se be revived in infla iston

The antiphlogistians also say, that the di of phosphorus is a proof of their theory; the pure air being i emitted fro phlogiston, that there is of dry flesh containing it; since the produce of the solution of it in nitrous acid, and its effect upon the acid, are the saistication of the acid

Their proof that water is deco steam over hot iron, inflammable air (which they suppose to be one constituent part of it) is procured; while the other part, viz the oxygene, unites with the iron, and adds to its weight But it is replied, that the inflaiston of the iron, united to part of the water, as its base, while the remainder of the water is imbibed by the calx; and that it is ene, that is retained in the iron, is evident, fro recovered when this calx of iron is revived in inflammable air, in which case the infla the place of the water, by which it had been expelled

In answer to this it is said, that the pure air expelled fro with the inflammable air in the vessel, recomposes the water found after this process But in every other case in which any substance containing pure air is heated in inflah the inflammable air be in part imbibed, some _fixed air_ is produced, and this fixed air is composed of the pure air in the substance and part of the inflammable air in the vessel Thus, if _minium_, which contains pure air, and _massicot_, which contains none, be heated in inflammable air, in both the cases lead will be revived by the absorption of inflammable air; but in the former case only, and not in the latter, will fixed air be produced The calx of iron, therefore, having the same effect with massicot, when treated in the same manner, appears to contain no more pure air than massicot does

Besides this explanation of the facts on which the new theory is founded, which shews it to be unnecessary, the old hypothesis being sufficient for the purpose, soed, as inconsistent with the new doctrine

If the calx of iron ree of heat, be reat quantity of infla to the new theory, neither of these substances contained any water, which they in of it But this fact is easily explained upon the doctrine of phlogiston; the water in this calx uniting with the phlogiston of the charcoal, and then for inflammable air; and it is the same kind of inflammable air that is made from charcoal and water

Also the union of inflaether by means of the electric spark, produces not pure water, as, according to the new theory, it ought to do, but _nitrous acid_