050 An Effay on Bhaching. 



fear of their lofing their properties by the way. I have al- 

 ready mentioned the extreme volatility of the liquid oxygen- 

 ated muriatic arid, and the almoft impotobility of transport- 

 ing it without {he lofs of nearly one-half of its firength; and 

 however little it may be fhaken in its pafTage, the acid gas 

 will entirely efiape. We (hall {how hereafter the method of 

 preparing and employing thefe muriates in bleaching. 



Of Potafh. 



The fubftance known in commerce under the name of 

 petajb, and which a£ts fo Important a part in the proeels of 

 bleaching, is a faline matter produced by incinerating plants 

 or wood, and lixiviating, concentrating, and calcining the 

 allies. The ufc of ley or afhes was known in the remote ft 

 periods; but the Germans were the firft who taupht us to 

 concentrate the fait diffufed throughout the water of the 

 folution, and to which (hey gave the name it now bears, 

 from the vetfels employed in the fabrication of it, viz. pot* 

 ajbesy or potafh. 



Though potato be very common in nature, it is the vege- 

 table kingdom which prefents it to us in the greatest abun- 

 dance. Chemifts are divided in regard to the quetiion, 

 Whether this fait exifts completely formed in the plants, or 

 is produced by the union of certain principles during the 

 combuftion ? It is fufficient for the bleaeher to know how 

 it is obtained, and to be acquainted with its moft ftriking 

 properties; for its chemical compofition is entirely unknown. 



The method of obtaining potafh is as follows: — Burn 

 herbs of every kind, except marine plants, or fuch as grow 

 on the fea fhore ; then lixiviate the afhes and evaporate the 

 folutions, by which means you will have a faline refiduum : 

 calcine this faline fubftance in a reverberating furnace, and 

 the product will be potato. This fubftance, as foon as it is 

 taken from the furnace, attracts the humidity of the atmo- 

 fphere ; or, to fpeak correctly, it endeavours to faturate itfelf 

 with carbonic acid : in this ftate it forms what the bleachers 

 call mild alkali ; it is then more detergent than foap, and lefs 

 fo than caullic alkali. Potafh is exceedingly foluble in water; 

 it requires little more than half its weight to diflblve it. The 

 potafh of the mops is often adulterated with other faline fub* 

 fiances, and commonly with the fulphate of potato, which 

 is purchafed, at a low price, by the makers of aquafortis, in 

 rlafs-houfes, &c. This fait degrades the quality of it, and, 

 by its little folubility in water, retards the operation of 

 bleaching. This fraud may he detected by one property; 

 for> as^fixtcen parts of water are required to difloive one of 

 4 this 



