Essay on the Analysis of Soils. 



53 



accurately weighed. The sum of them ought to be equal to the 

 original portion of soil subjected to analysis after the water was 

 driven off ; but there always is a loss, even with the most expe- 

 rienced analyser. This loss will be principally in the finer parts, 

 which are dissipated in the operation. 



But the analysis is not yet completed : we have separated 

 the sand, clay, and humus ; but there may be a portion of 

 carbonate of lime, in the form of sand, or of finely- divided earth 

 mixed with the other earths. To ascertain this, each portion, 

 excepting the humus, is put into a separate cup, and a little 

 muriatic acid, diluted with four times its weight of water, is 

 poured on it. If there is any effervescence, it shows the pre- 

 sence of carbonate of lime ; diluted acid is then added gradu- 

 ally, as long as the effervescence is renewed by the addition. 

 When this ceases, and the water continues to have an acid taste, 

 more pure water is added, and each portion separately filtered, 

 dried, and weighed. The loss of weight in each gives the 

 quantities of carbonate of lime dissolved by the muriatic acid, 

 and which has passed with the water in the form of muriate of 

 lime.'^ The different weights being now collected, the result of 

 the operations may be set down. 



There may be many mineral substances in the soil, which this 

 mode of analysing will not detect ; and some of these may 

 materially affect the fertility. In most cases there will be some- 

 thing to indicate the presence of metals. Iron abounds in most 

 soils : when the quantity is considerable it Avill be detected by 

 pouring a decoction of gall-nuts into the water which has washed 

 the earth ; it will immediately become of a bluish dark colour. The 

 other metals are not of frequent occurrence. Sulphate of lime or 

 gypsum, and also magnesia, are found in some soils ; but the 

 separation of them can only be effected by those who are well- 

 acquainted with chemistry : they fortunately occur very seldom, 

 and the places where they are found are generally well known. 

 For all practical purposes it is sufficient to ascertain the propor- 

 tion of sand, clay, carbonate of lime, and humus which any soil 

 contains. 



Many soils which have been highly manured contain por- 

 tions of undecomposed vegetable substances, and fibres of roots; 



* It may be objected to this mode of ascertaining the carbonate of lime, 

 that the muriatic acid will dissolve iron, and a portion, however small, of 

 alumina, as well as carbonate of lime, and that the collecting the carbonic 

 acid evolved is a more exact measure of the quantities of the carbonate. 

 This may ,be admitted, but we repeat that we only propose a simple and 

 easy analysis, which will approximate to the truth, and not by any means a 

 perfect one. We hope some more perfect, and no less simple, analysis will 

 be invented by those who are masters of the science of chemistry. 



