VOL. XLV.] PHILOSOPHICAL TRANSACTIONS. 5/8 



that afford a large quantity of it, but make a bad kind of potash, at least for 

 many purposes, on account of a neutral salt with which they abound. This 

 seems to have been the case of the potash made in Africa, in a manufacture of 

 that commodity set up there by the African company, which Mr. Houston, who 

 was chiefly concerned about it, tells us, in his Travels, proved so bad, on account 

 of a neutral salt it contained, that the manufacture was left off on that account; 

 or perhaps from their not knowing how to make it rightly. What those veget- 

 ables are that aflbrd this kind of ash, is not well known, if it be not fern, and 

 some sea-plants. 



Whatever vegetables are used, should be fresh or green, and nowise rotten, 

 dried, or decayed. They should likewise be burnt to ashes by a slow fire, or in 

 a close place; otherwise, when they are burnt in the open air by a strong fire, 

 great quantity of the ashes is consumed in smoke, by the saline and terrestrial 

 parts being carried up in fumes, before they are separated from these exhalable 

 parts by the action of the fire. For the difference between burning wood in a 

 close place and the open air, is so great, that the quantity of ashes obtained from 

 one is more than double the other. This we learn from the experiments of 

 Lundmarck hereafter mentioned, who tells us, he burnt a quantity of birch in a 

 close stove, from which he obtained 5 pounds of ashes; whereas the same quan- 

 tity of the same wood burnt in the open air, yielded only 2 pounds. .> 



It is for this reason, that most people who make potash, bum their wood in 

 kilns, or pits dug in the ground; though the Swedes burn it in the open air, as 

 the author abovementioned informs us. This first step, or the burning the wood 

 to ashes, seems to be taken by many for the whole process of making pot-ash; 

 for those who pretend to have learned this art in Russia, as well as Lemery and 

 some other authors, hardly give us any other account of it. But, in order to 

 convert the ashes, prepared in this or any other manner, to what is called pot- 

 ash, there are many different ways practised in different countries, which make 

 as many different kinds of potash, that are all to be found in our markets, and 

 have all their respective uses. 



1 . The first of these is commonly called pearl-ashes by our people, who import 

 great quantities of it from Germany. This is no other than the lixivial salt of 

 wood-ashes, extracted by making a strong lie of them, and by evaporating it to 

 dryness, in a manner that is well known, and sufficiently explained by Kunkel 

 in his art of making glass, also by Boerhaave, and many others. 



2. But the art of converting these wood-ashes into potash, without this tedious 

 process of elixiviation, is only practised in Russia, Sweden, and other northern 

 countries, where it has been lately disclosed by one Lundmarck, who tells us he 

 had often made it himself, in the manner he now describes. This account is 

 contained in an academical dissertation on this subject at Aboe in Sweden, an(i 



