150 An E/Jay on Bleaching, 



the workmen call dead ley, bv faturating the alkali with 

 acids, arid in that manner obtaining it in the form of a 

 greenifh precipitate, which he carefully warned, he made 

 the ft/lowing experiments to determine the action of alkalies 

 upon it: 



Eight grains of it were digefted in a folution of cryftallized 

 foda faturated at the temperature of oo ' of Fahrenheit : the 

 folution inftantly afliimed a dark brown colour. Two mea- 

 fures of this folution, weighing each 275 grains, were not 

 entirely diflblved by this fubftance; but two rneafures of a 

 folution of potafh diflblved the whole of it. 



One meafure of cauftic foda, the fpecific gravity of which 

 was 1-053, diflblved almoft: the whole of it, leaving only a 

 white reiiduum. 



One meafure of cauftic potafli, the fpecific gravity of which 

 was 1*030, diflblved the whole of it. 



One meafure of an alkaline fulphuret, the fpecific gravity 

 of which was I'l-o, dilTolved the whole matter. 



One meafure of ammonia diflblved alfo a portion of this 

 fubftance. 



Though tbefe exoeriments were fufficicnt to fatisfy Kir- 

 wan's doubts, he thought it neceflary to repeat them with 

 the faline fubftances ufually employed in bleaching as well 

 as with foap. 



He diflblved, therefore, an ounce of common foda, and as 

 much Dantzic potafb, each in fix ounces of diftiHed water: 

 eight grains of the green matter were put into a meafure of 

 an ounce of each folution, and then digefted for three hours 

 and a half in a heat equal to 180' of Fahr. The diflblving 

 power of the Dantzic potafli was fuperior to that of the foda; 

 for, an ounce of the folution of foda was flill required, and 

 half an ounce only of the folution of potafli, to diflblve the 

 whole of the fubflance. 



An ounce of white foap was diflblved in 18 ounces of di- 

 ftilled water. The folution was turbid, and it could not be 

 rendered tranfparent but by heating it almoft to the point of 

 ebullition, and then the operation was difficult; for when 

 the liquor, by chance, began to boil, it was thrown to the 

 di (lance of more than three feet from the matrafs. Three 

 ounces of this folution were required to diflblve eight grains 

 of the colouring matter. 



In order to compare the refpecYive flrength of thefe folu- 

 tions, it mufl be obferved, that an ounce of the foda of the 

 Ihops contains only 114 grains of pure foda: fuppofe the 

 folution to have been made in fix ounces of water, each 

 ounce of water will contain 19 grains of pure alkali, while 



an 



