FIXED ALKALIES. 



171 



The salt obtained by these operations loses by calcina- 

 tion, in order to convert it into pearlash, 25 or 30 per cent. 

 of its weight. 



The results of the experiments made by Kirwan upon 

 1000 lbs. of each of the vegetables assayed, are as follows. 



Table of Mean Results of the Experiments of Messrs. Kir- 

 wany Vauquelin, and JPertuis, upon 10,000 parts of each 

 plant. 



Elm 39 of potash. 



Oak 15 



Beech 12 



Vine 55 



Poplar 7 



Thistle 53 



Fern 62 



Cow thistle 196 



Wormwood 730 



Vetches 275 



Beans 200 



Fumitory 790 



In selecting plants to burn for potash, it is advisable to 

 choose those that contain the most of it ; grasses, leaves, 

 the stalks of French beans, of peas, melons, gourds, cab- 

 bages, artichokes, potatoes, maize, and garget, are very 

 rich in this alkali. The plants are first dried, and then 

 burned, and the ashes leached. 



