CHEMISTRY. 57 



others absorb more water from the atmosphere, and are dis- 

 solved in it, these are called deliquescent salts. 



Salts may effervesce or deliquesce without destroying their 

 peculiar qualities or the chemical union between the acid and 

 base. Salts dissolved by water again crystalize when the 

 water is evaporated. The crystals of some salts are very 

 small, as in epsom salts, in others they are large, as in chro- 

 mate of potash. 



ORGANIC ELEMENTS OF PLANTS. 



Organic bodies possess a much greater complexity of com- 

 position, than substances of mineral origin. The organic 

 bodies are distinguished from the inorganic by the nature of 

 their elements : the products of the vegetable kingdom surpass 

 in number and variety those of the mineral, but still those of 

 the former consist almost exclusively of six elements, viz : car- 

 bon, oxygen, hydrogen, nitrogen, sulphur, and pkospkortt?: of 

 these six, carbon alone exists in all bodies of both animal and 

 vegetable origin. Sulphur and phosphorus are met with but 

 seldom : iodine and bromine exist in marine plants and 

 sponges; besides these, plants contain in most cases, iron, 

 silicon, calcium, potassium, magnesium, manganese, and some- 

 times fluorine. These are called the ultimate elements of 

 plants, because they are the final result of analysis, and 

 cannot themselves be reduced to a more simple form, or sepa- 

 rated into other elements. 



These combine in such a manner as to form the various 

 substances, such as starch, gum, sugar, and an almost endless 

 variety of others found in plants. These latter are called 

 organic products, or immediate or proximate elements, because 

 they are more easily separated and obtained without a rigid 

 analysis. As a general rule, bodies most complex in their 

 number of elements and simplicity of equivalent relations, are 

 the weakest, and least capable of resisting those disturbing 



