ORGANIC Matters op the soit,. 231 



(o solutions of liumatcs or ulinates of the alkalies, precipi- 

 tates are formed in -which the acid is combined Loth with 

 an alkali anl an earth or oxide. These double salts are 

 insoluble or nearly so in vater. 



Solutions of alkalies and alkali carbonates decompose 

 them into soluble alkali humates or ulmates, and the 

 earths or oxides are at least partially held in solution by 

 the resulting compounds. 



Mulder describes the fuUowing experiments, which justifj' the above 

 conclusions. "Garden-soil was extracted with dilute solution of car- 

 bonate of soda, the soil being in excess. The solution was filtered and 

 preeiintateil bj- addition of w:Uer, and the precipitate was washeil and dis- 

 solved in a little ammonia. Thus was olMained a dark -brown solution 

 of neutral humate of ammonia. The solution was rendered perfectly 

 colorless by addition of caustic lime — basic humate of lime is therefore 

 perfectly insoluble in water. 



"Chloride of calcium i-endcred the ?olntion verj' nearly colorless^ 

 neutral humate of lime is almost entirely insoluble. 



"Calcined mai^nesia decolorized the solution perfectly. Chloride of 

 magnesium made the solution very nearly colorless. 



"The sulphates of protoxide and peroxide of iron, and sulphate of 

 manganese, decolorized the solution perfectly. 



"These decolorized liquids were made bi-own again by agitating them 

 and the ju-ecipiiated humates with carbonate of ammonia." 



Apocrenatcs and Crenates. — According to Mulder, the 

 crenates and apocrenates of the soil nearly always contain 

 ammonia — are, in fact, double salts of this alkali with lime, 

 i.on, etc. 



The (ipocrenotes of the alkalies are freely soluble; 

 those of the oxides of iron and manganese are moderately 

 soluble ; those of lime, magnesia, and alumina, are in- 

 soluble. 



The crenates of the alkalies, of lime, magnesia, and 

 protoxide of iron, are soluble ; those of protoxide of iron 

 and manganese are less soluble ; crenate of alumina is 

 insoluble. 



All the salts of these acids that are insoluble of them- 

 selves are decomposed by, and soluble in, excess of tlie 

 alkali-salts. 



