272 VII. EARTHS AND ALKALIES. 



ALKALIES AND THEIR CARBONATES. 



As the two subcarbonates of soda and of potash are sold in a 

 sohd form, their strength is attempted to be ascertained by the 

 quantity of sulphuric acid that a solution of 100 gr. of either of 

 them requires for its saturation : this operation is called alkali- 

 metry, and tubes graduated into 100 parts, and containing the 

 necessary quantity of acid to saturate 100 grains of the pure sub- 

 carbonates are used, called alkalimeters ; but as the sulphuric acid 

 acts upon the sulphates and sulphurets of these alkalies, and 

 which are usually present, the essay is not a whit more accurate 

 than the method of the German soap boilers, who merely pour a 

 quart of water upon a pound of ashes, and then putting in a piece 

 of Dutch soap, add water in small portions until the soap sinks. 

 The ashes are the stronger as they require more water before the 

 sinks. 



POTASH. 



AsH BALLS, Cineres herharurtu Principally the ashes of fern, 

 made up into balls : used for washing instead of soap, and to 

 clean paintings. 



PoT-ASH, Alumen catinum. From land plants burned to ashes, 

 the ashes elixated with water, and the ley evaporated to dryness. 

 From America. 



Peaul-ash, Potasse de Neio Yorck, Potasse rouge d'^Amerique^ 

 Cineres perlati. From pot-ash, by calcination, by a gentle heat 

 to avoid melting, solution in water, filtration, and evaporation, 

 stirring it all the time to granulate the salt. From America. — 

 Burnt lees ofwine^ Cendres gravellees, Cinis irifectorius, C, fcEcum^ 

 Cineres clavellatiy Alumen fcecum. Potasses subcarbonas impurus, 

 Potassa impura. From the ashes of lees of wine, grape cake, 

 and vine twigs, very pure ; preferred by the continental dyers. 

 From France. This is used for preparing the subcarbonate for 

 medical uses. 



Salt of tartar, Sal tartaric Kali ppm. e tartaro, Kali e 

 tartaro, Subcarbonas potassce purissimus^ Potasscz subcarbonas e 

 tartaro. Burn argol in a crucible, powder and calcine till it is 

 nearly white ; dissolve in water, filter and evaporate. Composed 

 of 6 pot-ash, 2*75 carb. ac, with 2*25 water : equiv. 11 ; 100 gr. 

 saturate 70 of oil of vitriol. 



Salt of wormwood, Sal absinthii. Wormwood burned to 

 ashes, dissolved in water, the solution filtered, and evaporated to 

 dryness. 



