No. 216.] 731 



acid. The principal bases are Soda, Potassa, Lime and Magnesia, 

 which enter into the coniposition of all fertile soils. The acids with 

 which these ordinarily combine are the Carbonic, the Sjlphuric and 

 Phosphoric. By burning plants, these combinations appear in the 

 ashes. An examination of the properties of these principal sails, 

 and of their components, sheds a great light upon this subject. Let 

 us begin with the ashes. These are discovered to be metal ic oxydes, 

 the pure metals of which were obtained by wSir Humphrey Davy, and 

 they are denominated respectively, Potassium, Sodium, Calcium and 

 Magnesium, and from Barytes, Barium, &c., &c. But Potassium, 

 which is the one most easily obtained, may be taken as a type of the 

 class. It is a glittering metal, much like silver, but clear as water. 

 It has some qualities in common with Sodium; when a current of 

 water is passed over it, it is decomposed with great rapidity, devolv- 

 ing its oxygen. It often changes red color to blue. It combines with 

 other acids, forming neutral salts, which are obtained by evapora- 

 tion. The other alkaline metals follow the same process, but not so 

 energetically as Potassium. The proportions in which they continue 

 are 40 parts Potassium, and 8 of Oxygen, making 48 of Potassa; 

 24 parts of Sodium with 8 of Oxygen, making 32 of Soda. 



Knowing the great importance it is to a farmer to know what 

 amount his soil contains of Potassa or of Soda, we present them dis- 

 dinctly. Take a portion of the soil and put it into boiling water, and 

 then strain the whole through a filter. The water will extract all 

 the soluble portions; then dry by evaporation, and the salt remaining 

 will show by its form, its solubilit}-, and the action of the air upon 

 it when exposed, what base it contains. That base will generally 

 be found combined with sulphuric acid. When Sulphate of Potassa 

 is present, it will be discovered by its slow solution and its perraa-. 

 nency when exposed to the air. Some plants receive from the soil 

 minute portions of alkili, while others absorb an immense quantity. 

 Some plants, mustard for example, contain a considerable quantity of 

 sulphur, which combining with Oxygen, developes the offensive gas, 

 Sulphuretted Hydrogen, as is found in fire-arms, sometimes neglected, 

 and in putrified eggs. To this is owing the nauseous smell of water in 

 which some vegetables have been cooked. So with the water near 

 the mouths of rivers, especially on the coast of Africa. The copper 

 of ships anchored there, rapidly decays, and this is the attributed 

 cause of the unhealthiness of those shores. The best test of its pre- 

 sence is Sugar of Lead in solution, which in a short time shows it 

 by producing Sulphuret of Lead. Sulphuretted Hydrogen is then un- 



