CHAPTEE VIII, 



Experiments with the chlorides of potassium and with common salt, or chloride 

 of sodium. Composition and general properties of the chlorides of potassium, 

 sodium, calcium and magnesium, of the fluoride of calcium, and of muriatic 

 acid. Suggestions for comparative experiments with the chloride of potas- 

 sium applied alone. Results of experiments with common salt applied alone. 

 Influence of circumstances upon the observed effects of common salt when 

 applied directly to the land. Theory of the action of common salt when 

 applied alone. 



1. Composition and general properties of the chlorides of 

 potassium, sodium, (common salt,) calcium, and magnesium, of the 

 fluoride of calcium, and of muriatic acid. 



The substances above named contain their several elements 

 in the proportions represented in the following table : 



Name. 



Chloride of potassium, 

 sodium, 

 calcium, 

 magnesium, 



Fluoride of calcium, 

 (fluor spar,) 



Muriatic acid, 



Consists of, in 100 parts 



Chlorine 47.47 Potassium 52.53 



60.34 Sodium 39.66 



63.36 Calcium 36.64 



73.65 Magnesium 26.35 



Fluorine 47.73 

 Chlorine 97.26 



Calcium 

 Hydrogen 



52.27 

 2.74 



The substances called potassium, sodium, calcium, and mag- 

 nesium, in the above table, are metals, white, soft, very light, 

 and having a bright silvery lustre when newly cut with a knife. 

 They speedily tarnish in the air, however, by combining with 

 the oxygen of the atmosphere, and forming respectively the 

 compounds known by the names of potash, soda, lime, and mag- 

 nesia. 



1. Chloride of potassium is a white salt, which crystallises in 

 cubes ; is without smell ; has a saline taste, resembling that of 

 common salt ; undergoes no change in the air ; crackles when 



