SODA AND AMMONIA. 15 



SODA. 



Both potash and soda are bases for organic and mineral acids, in which combination 

 they are connected with the growth and development of plants. The tubers of potatoes 

 require both pot£ish and soda, and, when grown in a suitable soil, they form a valuable 

 food : if, however, they vegetate in the open air, a poisonous alkali is formed from the 

 elements of the tuber, in which there exist mere traces of potash and soda. 



The great source of soda is sea water and saline springs, where it is in combination with 

 chlorine. It is also found in mineral bodies, in the same relations as those of potash : 

 hence soils may be supplied with soda by the decomposition of slates, shales and clays. 



It will be observed, on consulting the analyses, that soda is in less proportion in soils, 

 rocks, and in the ash of plants, than potash. Plants growing in sea water and near brine 

 springs, as at Salina and Syracuse, contain soda. The Salsola kali is common about the 

 salt-pans and fields moist with chloride of sodium. It here finds its proper food, and is as 

 flourishing as upon the shores of the Atlantic. 



In rocks the percentage of soda is sometimes as high as 1 1 • 48, as in albite, a common 

 variety of felspar ; in mica, it is only from 3 to 5. Notwithstanding the apparent small 

 percentage of soda in rocks and soils, we see that it has accumulated in immense quantities 

 in some locations, as in the rock salt of Cheshire in England, Cracow in Poland, &c. 

 The sea, however, forms the great reservoir. 



It is maintained by many that potash and soda may replace each other, in case of an 

 absence of either ; that marine plants which naturally require soda, if cultivated far inland, 

 take the vegetable alkali in place of the mineral. This, however, is a forced state ; and 

 the probability is, that in these cases the plant in a few years would cease to vegetate. 



AMMONIA, VOLATILE ALKALI, HARTSHORN. 



Ammonia, like pttash and sotla, is an original constituent of the globe ; but unlike those 

 alkalies, it is constantly produced and destroyed by the aflinity of the elements which 

 compose it. Nitrogen and hydrogen being its elements, may unite whenever they exist 

 in a complex substance, when that substance is decomposed. It is exhaled from animal 

 and some vegetable matters in the process of decay, during which it is probably formed 

 by the union of its elements, but in which it did not exist as ammonia when the decay 

 began. 



Ammonia is also exhaled from the deep interior of the earth. Its salts condense in 

 and upon the fissures of the rocks near volcanic vents. Its vapor rises from the lagoons 

 of Tuscany, in company with boracic acid. This fact, however, does not prove that it 

 exists in masses and reservoirs in the interior of the earth : it may be formed in its boweb, 

 by the decomposition of water acd other bodies in which nitrogen is an element. 



The importance which ammonia takes in the processes of agriculture, arises from the 



