AGRICULTURAL CHEMISTRY, 19 



24. Manganese. — A metal resembling iron, but of a 

 darker color and more brittle. It is never found in 

 its pure state ; is prepared with great difficulty ; and 

 is in that state of no sort of use. It is found, com- 

 bined with oxygen, in nearly all soils ; and from the 

 soil it enters into plants. 



25. Potassium. — A brilliant, silver- white metal, with 

 a high degree of metallic lustre ; the metallic basis of 

 potash; burns with great brilliancy if thrown upon 

 cold water, or ice even; the lightest of all metals, 

 being about 4-5 as heavy as water. 



26. Sodium. — A white, silvery metal ; ihe metalHo 

 basis of soda; burns if thrown upon warm water; 

 9-10 as heavy as water. Potassium and Sodium are 

 the only metals- known that are lighter than water. 



27. Calcium. — A yellowish-white metal, the basis 

 of lime. It is from calcium, the metallic basis of linpie, 

 that a limy soil is called calcareous. 



28. Magnesium. — A white, shining metal, the basis 

 of calcined Magnesia. 



29. Aluminum. — A metal in the form of a gray 

 powder ; not easily melted ; the metallic basis of clay 

 and of clay soils. 



30. Of these 15 elements, 4, when in an uncombined 

 state, are gases, viz.: Oxygen^ chlorine^ hydrogen^ and 

 nitrogen. The remaining eleven are solids at ordi- 

 xjary temperatures. 



