"22 SULPHURIC AND PHOSPHORIC ACIDS. 



stream of it poured gently into a cup of \vater from a 

 small distance above the surface, can be seen to sink 

 directly to the bottom. When agitated so as to mingle 

 it with the water, the mixture becomes quite hot, be 

 cause a chemical union takes place between the two 

 liquids. 



e. This acid, except in such cases as the above, is 

 always found in a state of combination with some other 

 substance, and then can not be recognized by any of 

 the properties which I have mentioned. In some of 

 these forms of combination, it is very abundant. One 

 of them, and an important one to the farmer, is gyp 

 sum, or plaster of Paris. This, as is well known, is a 

 solid, and has no acid taste : it, however, consists of 

 sulphuric acid united with lime, forming what is termed 

 by chemists sulphate of lime. In every 100 Ibs. of 

 plaster of Paris are about 33 Ibs. of sulphuric acid, 

 46 Ibs. of lime, and 21 Ibs. of water. 



Epsom salts consist of sulphuric acid and magnesia; 

 alum, of sulphuric acid, alumina and potash. From 

 all of these the acid can be separated by chemical 

 means. It is used largely for various manufacturing 

 purposes, and is made by burning sulphur (brimstone), 

 with certain precautions, in large leaden chambers. 

 This acid will be subsequently seen to be a substance 

 of great importance for various purposes in agriculture. 



i* Not less important is the next body on our list, 

 ^-2 ^phosphoric acid. It is also very sour, and is usually 



. yseen as a white powder. If a stick of phosphorus is 



= burned, white fumes are seen to rise in large quantity. 

 The phosphorus unites while burning with the oxygen 

 of the air, and forms phosphoric acid. If these white 

 fumes are passed through water, it w r ill become sour, 

 as it dissolves the acid : they may also be condensed 

 on a cold glass plate. 



a. This body can be shown in a yet simpler manner 



