124 PRIZE ESSAY: 



situations contain an abundance of common salt, but every sea 

 breeze bathes the growing crops near the coast in moist air, 

 holding in solution a quantity of common salt. 



222. What will be the chemical action of common salt upon 

 the ammonia of fogs and dews ? The form in which the ammo- 

 nia is present is that of a carbonate ; its exact constitution is not 

 of the slightest consequence. As a carbonate the chemical 

 changes which would occur are as follows : 



Common salt or chloride of sodium, acting upon a carbonate 

 of ammonia, would produce bi-carbonate of soda, chloride of 

 ammonium, and free ammonia. The free ammonia would com- 

 bine at once with free carbonic acid, and be again decomposed, 

 and another portion fixed by the common salt present in the 

 moist air, and so on. The real effect of the salt is, then, to fix 

 the ammonia of fog, mist or dew, and in that way it is most pro- 

 bable that this substance operates so beneficially in- arresting 

 mildew and rust. 



223. Johnson, in his " Essay on Salt," explains the action of 

 this agent in the following way ' " The certainty and celerity of 

 its operation I account for thus : the mildew, it is now well as- 

 certained, is a parasitical plant of the fungus tribe, the principal 

 constituent of which tribe is water ; when salt, therefore, is ap- 

 plied to them, the aqueous particles are immediately absorbed, 

 and their vitality destroyed." The objection to this view is, 

 that in the experiments made to test the effect of salt on mil- 

 dew, it was used in a state of solution, in the proportion of one 

 pound of salt to one gallon of water, so that the salt was fully 

 saturated with water, and could not possibly have acted on the 

 fungi in the manner described above. It might have acted as a 

 poison, but its action arose, no doubt, from the fixation of the 

 ammonia, so stimulating to mildew and rust, as described in the 

 preceeding paragraph. 



