580 PHILOSOPHICAL TRANSACTIONS. [aNNO 1748; 



nor seen it done; and those who have tried this or any other way, find more dif- 

 ficulty in it than they at first imagined, we shall suspend our judgment about it, 

 till we see it fairly tried, lest we should deter some from making useful experi- 

 ments of it, or lead others into fruitless and expensive attempts. 



By the various ways of making potash above mentioned, and the different 

 materials it is made of, there appear to be many different kinds of it, that have 

 as different qualities. It would lead us too far beyond our present design, to give 

 a particular account of each of these ; but as they are used in many of our manu- 

 factures, it seems worthy inquiry, to know what sorts are generally used, and 

 what are the fittest to be used in them. 



The workmen in England make 2 general kinds of it, which they distinguish 

 by the names of pearl-ash and potash. The first is a mere lixivial salt, which is 

 supposed to be the only ingredient of any efficacy in potash ; but on trial there 

 is found to be a great difference between them, especially in making soap. The 

 salt is so weak in the pearl-ash, that it does not entirely dissolve and unite with 

 the fat. The reason seems to be, that these salts are dissolved in water, in order 

 to extract them, by which they lose many of their caustic igneous parts ; whereas 

 in potash, the salts are calcined and fluxed in an open fire, with the ignited 

 terrestrial parts of the ashes, which makes them more sharp and corrosive : they 

 are likewise incorporated with the coal, and fuliginous parts of the vegetables 

 they are made of, or with the resinous parts of fir, which gives them the sul 

 phureous quality above mentioned, and makes a kind of soap of tartar, or hepar 

 sulphuris, in all potash ; which makes these salts so ready to dissolve, and in- 

 corporate with oil, or other pinguious substances. 



This is perhaps the reason, why the cineres russici are ordered for this pur- 

 pose, instead of a mere lixivial salt, by the College of Physicians in their late 

 dispensatory. The soap made of them must be impregnated with their heating 

 sulphureous quality, which will make it more aperient and detergent, but not so 

 mild and soft as some others ; by which it may be more fit for obstinate and in- 

 durated obstructions, but will be more offensive to the stomach ; which is much 

 complained of by some people, who take large quantities of tlie sharper kinds 

 of soap. 



But, to consider potash as a commodity in trade and manufactures, which is 

 its chief use ; it appears, that the people in England not only have it at a dear 

 rate, but the worst sorts of it, at least for most purposes ; which cannot but 

 have a proportional influence on their manufactures : for it is generally of as 

 great, and some sorts of a greater value in their markets, than a pure lixivial 

 salt ; notwithstanding the small quantity of such salt in ashes, and the trouble 

 and expence of extracting it ; which seems to be occasioned by their not know- 

 ing how to convert ashes into this commodity ; for in Sweden, where this art is 



