570 PHILOSOPHICAL TRANSACTIONS. [aNNO 1748. 



the stones they find on the shore, in a c) Undrical form, and about 1 feet or less 

 in diameter. In this they first burn a small parcel of the herb, and before it is 

 reduced to ashes they throw on more, till the kiln is full, or their materials are 

 expended. This is said to reduce the ashes to a hard and solid cake, by the heat 

 of the kiln, and quantity of salt in the herb, which makes what is commonly 

 called kelp-ashes. 



There are some other ways of making potash, suggested by several persons, 

 which appear to be more easy and ready than any of the abovementioned ; for 

 which reason they are apt to be tried by those who make attempts of this kind. 

 These are deduced from what they reckon the nature and properties of this pro- 

 duction ; and there is no doubt, but if that was well understood, it might afford 

 some insight in the way of making it. For this reason we made the following 

 experiments with the best Russia potash, in order to discover its nature and 

 properties, and how they are most probably communicated to it; that we might 

 see what we are to make; in order to imitate the best, or to make what is ac- 

 counted good potash. 



1 . Russia potash, as it is brought to us, is in large lumps, as hard as a stone, 

 and black as a coal, incrusted over with a white salt, that appears in separate 

 spots here and there in it. 1. It has a strong fetid sulphureous smell and taste, 

 as well as a bitter and lixivial taste, which is rather more pungent than other 

 common lixivial salts. 3. A lixivium of it is of a dark green colour, with a very 

 fetid sulphureous smell, and bitter sulphureous taste, somewhat like gunpowder, 

 as well as sharp and pungent like a simple lixivium. 4. Though it is as hard as 

 a stone, when kept in a close place, or in large quantities together in a hogshead; 

 yet, when laid in the open air, it turns soft, and some pieces of it run per deli- 

 quium; while most other kinds of potash only turn friable, and crumble in the 

 open air. 5. It readily dissolves in warm water, but leaves a large sediment of a 

 blackish grey colour like ashes, which is in a fine soft powder, without any dirt 

 or coals in it, that are to be observed in most other kinds of potash. 6. As it 

 is dissolving in water, there is scummed oflf from some lumps of it a dark purple 

 bituminous substance, like petroleum or tar, which readily dissolved in the lixi- 

 vium. 7- This, or any other true potash, or a lixivium made of them, will 

 presently tinge silver of a dark purple colour, difficult to rub oif; while a mere 

 lixivial salt has no such effect. 



8. Pieces of this potash boiling in water made a constant explosion like gun- 

 powder; which was so strong as not only to throw the water to some height, 

 but to lift up and almost overset a stone cup in which he boiled them. These 

 explosions were owing not so much to the included air, which some perhaps may 

 imagine, as to the sulphureous parts of the composition expanding and flying off; 

 for this boiled lixivium had neither the green colour, nor fetid sulphureous smell 



