VOL. LXI.J PHILOSOPHICAL TRANSACTIONS. 219 



found that it saturated as much as near 1^ oz. of the common gross barilla, in 

 the form it is commonly imported. He had it likewise tried by calico printers, 

 and it was found to answer all their purposes, and nearly in the same proportion 

 with respect to the gross barilla, as above mentioned, and he was told that it 

 was thought to answer better than any other salt they had ever tried. Most of 

 the neutral salts made with this alkali and acids, except the cubic nitre, keep 

 long without running per deliquium, even those made with vegetable acids ; for 

 most of the neutral salts made with vegetable acids, and with some of this salt, 

 which he had the honour to present to the r. s. in the year 1767, still remained 

 etitire, though kept only in a close drawer, in the same tea-cups and small 

 basins, v\'ithout any cover, as they were shown to the Society. 



He had not been able to learn in what particular place of the inland part of 

 Tripoli in Barbary this salt is found, nor how it is disposedof in the bowels of the 

 earth: but it should seem to run in thin veins, of about ^ an inch, or a little 

 more thick, in a bed of sea-salt ; for all of it that has hitherto been imported 

 into this country, is covered with sea-salt on each side. The one side is always 

 smoother than the other, and appears as if it had been the basis on which it 

 rested; the other, which should seem to be the upper side, is rougher, by the 

 shooting of the crystals. The pieces of the thin veins appear almost as if the 

 salt had been dissolved in water, and afterwards boiled up into thin crystallized 

 cakes, only that the crystals are much smaller, and disposed in a manner that 

 cannot easily be imitated by art ; for when this salt is dissolved, and evaporated 

 to a pellicle, and left to crystallize, it always shoots into crystals resembling those 

 of Glauber salt. 



Brown paper dipt into a solution of this salt, after it is dry burns almost as if 

 it had been dipped in a solution of true nitre, as Dr. Heberden had observed of 

 the salt got at the Pic of TenerifF; which shows that it contains more of an in- 

 flammable principle than the common vegetable alkali. There are great mines 

 of sea-salt in the country of Tripoli, the salt of which should seem to contain a 

 large proportion of this natron; for he was told that all the meat salted with it 

 acquired a red colour. 



This native alkaline salt having never been subjected to the force of fire, is 

 perfectly mild, and contains no caustic parts, as the barilla, and the common 

 potashes prepared by burning wood and plants, or the salts thrown out by vol- 

 canos commonly do; and therefore it will be found to be much more useful for 

 bleaching and washing linens, and for clearing and scowering cotton or woollen 

 stuffs, and for many other purposes, than any other alkaline salt hitherto known, 

 at the same time that it will answer every purpose for which the other kinds of 

 the fossil alkali are employed. 



When this salt is to be used for making rochelle or other neutral salts, or for 



p F 2 



