1 804* Experiments in the Atmlyznticn of Marl, i6^ 



TO THE CONDUCTOR OF THE FARMEU's MAGAZINE. 



Expcrhneftts in the Analy-zation of Marl, 

 By Sir Geo. S. Mackenzie, Bart. 



Thinking that A. S. may he more* fully convinced of the 

 truth of what I have already ftated rcfpeclingr the merhod ot 

 tryinj]j the qualities of limeftone, by being told the ufual pro- 

 cefles of a chemical analyfis, and in hopes that many of your 

 readers may be afTured of the fallacy of .rude experiments, in 

 dire<Sijig them in the purchafe and diftribution of lime or marl, 

 I beg leave to fubjoin the analyfis of marl, (not having limeftone 

 at hand) which is not given as perfe£lly -accurate, but merely to 

 (liow fuch of your readers as may not have (ludied chemidry, 

 the intricacy even in the analylis of a mineral, whofe decompo- 

 fition requires lefs dexterity than perhaps any other. 



Some of the marl being divided into portions of equal weight, 

 and allowed to dry for two days in the air, — on being again 

 weighed, they were found to be of different weights. Hence, 

 it is evident, that the r^^/ quantity of lime contained in any por- 

 tion of the marl, can be afcertained with certainty, only after the 

 marl has been properly dried. Attention to this circumlhance is 

 required in preparing any mineral for analyfis. 



When thrown upon melted nitre, the marl, in its natural 

 (late, detonated flightly. But a portion of the marl which had 

 been dried by a heat almofl red, fcarcely affected the nitre. 

 Melted nitre may be ufed as a teft (not a perfecSl one) for try- 

 ing the quality of any foil,' in refpe6l to the quantity of carbon- 

 aceous matter it may contain. According to the degree of de- 

 tonation, the quantity cf fuch matter may be in feme degree 

 judged of. 



One hundred grains of the marl, dried by a heat wliich made 

 the fides of the crucible barely red, loft, during their folution in di- 

 luted muriatic acid, 1^2 per cent, of their Wei-ghr. 100 parts of 

 carbonate of lime, contain 55 of earth, and 45 of carhoi)ic ncid ; 

 therefore, 32 per cent, of fixed air, indicates 39.1 of lime. 

 This then is the refult of the proccfs I have recommended in 

 my laft letter, and it comes very near the truth when cautioully 

 gone through. But the refult of tlie analyfis, Oiows the marl to 

 contain more lime than this. Therefore, either fome fixed air 

 was driven off in the drying, or the lime in this marl is not 

 guite faturated with the carbonic acid. Whichever of thefe 



S z cafes 



