Mr. Minish, according to the English writers, is entitled to this method of converting impure liquid ammonia into sal ammoniac. The following is an outline of his process. He suffered the impure ammoniacal liquor to percolate through a stratum of bruised gypsum, and as carbonate of ammonia is contained in the liquor, the fluid, which filters, would contain sulphate of ammonia, the carbonate of lime being insoluble. This sulphate he evaporated, and the dry mass, mixed with muriate of soda, was sublimed. If I am not greatly mistaken, however, although I have not the work to refer to, this process is described in Dr. John Pennington's _Chemical Essays_, a work published in Philadelphia, about 1792. Dr. Pennington's work, we may observe, is the first chemical book which was published in the United States, and contains numerous important facts and observations. That this process was known in Philadelphia, and used at the _Globe works_, or rather _Glaub works_, (from the circumstance that Glauber's salt was made there,) is within the recollection of many. I heard the late professor Wistar speak of this process, and of the economy in using gypsum. Mr. Lebanc (_Annales de Chimie_, vol. XIX.) invented a process, by which he brought the ammoniacal gas and muriatic acid gas in contact, in a chamber lined with lead. In one pot, he put common salt and oil of vitriol; in another pot, animal matter. Being conducted by pipes into the chamber, the gases united, and sal ammoniac was formed. Other improvements have been made, as obtaining ammonia from coal soot, &c. Ammonia is generated in artificial nitre beds, and is at first united with nitric acid; which compound is subsequently decomposed, as the process of putrefaction goes on, by the potassa, calcareous earth, &c. present in nitre beds. _See Nitrate of Potassa._ Sal ammoniac is ready formed in the soot of animal feces, twenty-six pounds of which yield six of the salt. According to Siccard, who published, in 1716, an account of the fabrication of sal ammoniac in Egypt, which Geoffroy, in the same year, proved to be a compound of the spirit of sea salt and volatile alkali, sea salt and urine were used in that country. The account, however, given by Lemery, in 1719, makes no mention of either sea salt or urine. Sal ammoniac is found native. It occurs in the vicinity of burning beds of coal, both in Scotland and England, and is met with in volcanic countries. When triturated with quicklime, it exhales ammonia, which is a characteristic of all ammoniacal salts. Sal ammoniac is often found in crusts of lava. Sir William Hamilton observes, that, in the fissures formed by the lava, this salt sublimes. He found, in the same locality, common salt.