These were all necessary conclusions from the above suppositions. Many of them appeared too improbable to deserve any further attention: some however, I found upon reflection, were already seconded by experience. Thus _Hoffman_ has observed, that quick-lime does not effervesce with spirit of vitriol;[7] and it is well known that the caustic spirit of urine, or of salt ammoniac, does not emit air, when mixed with acids. This consideration excited my curiosity, and determined me to inquire into the truth of them all by way of experiment. I therefore engaged myself in a set of trials; the history of which is here subjoined. Some new facts are likeways occasionally mentioned; and here it will be proper to inform the reader, that I have never mentioned any without satisfying myself of their truth by experiment, tho' I have sometimes taken the liberty to neglect describing the experiments when they seemed sufficiently obvious. Desiring to know how much of an acid a calcarious earth will absorb, and what quantity of air is expelled during the dissolution, I saturated two drams of chalk with diluted spirit of salt, and used the Florentine flask, as related in a similar experiment upon magnesia. Seven drams and one grain of the acid finished the dissolution, and the chalk lost two scruples and eight grains of air. This experiment was necessary before the following, by which I proposed to inquire into the truth of the first proposition so far as it relates to quick-lime. Two drams of chalk were converted into a perfect quick-lime, and lost two scruples and twelve grains in the fire. This quick-lime was slaked or reduced to a milky liquor with an ounce of water, and then dissolved in the same manner, and with the same acid, as the two drams of chalk in the preceding experiment. Six drams, two scruples and fourteen grains of the acid finished the saturation without any sensible effervescence or loss of weight. It therefore appears from these experiments, that no air is separated from quick-lime by an acid, and that chalk saturates nearly the same quantity of acid after it is converted into quick-lime as before. With respect to the second proposition, I tried the following experiments. A piece of perfect quick-lime made from two drams of chalk, and which weighed one dram and eight grains, was reduced to a very fine powder, and thrown into a filtrated mixture of an ounce of a fixed alkaline salt and two ounces of water. After a slight digestion, the powder being well washed and dried, weighed one dram and fifty eight grains. It was similar in every trial to a fine powder of ordinary chalk, and was therefore saturated with air which must have been furnished by the alkali.