218 PHILOSOPHICAL TRANSACTIONS. [aNNO 1771- 



they are alleged to have existed formerly; but it has long been found in Egypt, 

 and near Smyrna, and in other eastern countries, commonly mixed with earth, 

 in a floury or concrete form ; in some places pretty pure, in others more mixed.* 

 In the year 1764, Dr, Wm. Heberden gave an account of a salt of this kind, 

 found on the Pic of TenerifF, where there is a volcano; and added several very 

 ingenious experiments of the Hon. Henry Cavendish, to prove that the vegetable 

 alkali has a greater affinity with acids than the fossil or natron. It is probable 

 that this salt, got at the Pic of Tenerift", is the basis of sea-salt, whose acid has 

 first been dislodged, either by the force of fire, or by the acid of decomposed 

 sulphur, which has afterwards been attracted by a fresh phlogiston, and both 

 separated by the force of fire; though it is not at all impossible but that there 

 may be magazines of this fossil salt lodged native in the bowels of this mountain. 

 ^' Hitherto there had been no account of its being found any where native in a 

 crystalline form, and in large quantity ; and therefore he imagined that the fol- 

 lowing history would be agreeable to the R. s. In the year 1765, Mrs. White, 

 widow to the late consul White of Tripoli, on her return to this country, showed 

 Dr. D. M. a substance which, she said, had a very particular property of bubbling 

 up, or fermenting, when mixed with lemon juice. Immediately, on seeing and 

 tasting it, he suspected it to be a pure native natron, or fossil alkali ; and was 

 confirmed in this opinion, by mixing it with different acids; and he afterwards 

 had a few pounds of it sent home to him, and some gentlemen in the city had 

 imported some hundred weight of it. 



On inquiring into the history of this salt, he was told that it was brought 

 yearly to Tripoli, in large quantities, from the mountains in the inland part of 

 the country, and that it went by the name of Trona ; that the inhabitants some- 

 times took an ounce, or more of it, by way of physic, and that it commonly ope- 

 rated both as an emetic and purgative medicine; that the principal use they made 

 of it, was to mix it with their snuft^i to give it, what they think, an agreeable 

 sharpness; and that it was yearly sent to Constantinople, in large quantity, to be 

 employed for the same purpose. But so far as he could learn, the Turks are 

 entirely ignorant of its nature, and employ it for no other uses. It is well 

 known that this salt does not run per deliquium, but falls down into a white 

 floury powder, when exposed to the air; and that it makes a harder and firmer 

 soap than the common vegetable alkali, and is alleged to make a purer and finer 

 glass. 



This salt, which he had the honour to present to the r. s., was extremely pure, 

 dissolved entirely in water, leaving only a small quantity of a reddish earth be- 

 hind. He tried what quantity of acid I oz. of this salt would saturate, and 



• See HofFman, Phys. Chem. lib. ii- obs. 1. GeofFroy, Mater. Medica, part i. cap. 2. Dr. Shaw's 

 Travels, Excerpt, p. 55, and other authors.— Orig. 



