618 



F A R JNl E R S ' REGIS T E II 



[No. 11 



be often stirred, and suffered to remain for an 

 hour, or an hour and a hail', before it is examined. 



It' any carbonale of lime or of magnesia exist 

 in the soil, they will have been dissolved in this 

 time by the acid, which sometimes lakes up like- 

 wise a little oxide of iron ; but very seldom any 

 alumina. 



The fluid should he passed through a fdter ; the 

 solid matter collected, washed with rain water, 

 dried at a moderate iieat, and weighed. Its loss 

 will denote the quantity of solid matter taken up. 

 The wasliings must be added to the solution, 

 which, if not sour to the taste, must be made so 

 by the addition of fresh acid, when a liitle solution 

 of prussiate of potassa and iron must be nuxed 

 with the whole. If a blue precipitate occurs, it 

 denotes the presence of oxide of iron, and the so- 

 lution of the prussiate must be dropped in till no 

 farther effect is produced. To ascertain its quan- 

 tity, it must be collected in the same manner as 

 other solid precipitates, and heaied red ; the result 

 is oxide of iron, which may be mixed with a little 

 oxide of manganesum. 



Into the fluid freed iiom oxide of iron, a solu- 

 tion of neutralized carbonate ol' potash must be 

 poured, till all effervescence ceases in it, and till 

 its taste and smell indicate a considerable excess 

 of alkaline salt. 



The precipitate that falls down is carbonate of 

 lime ; it nmst be collected on the filter, and dried 

 at a heat below that of redness. 



The remaining fluid must be boiled for a quar- 

 ter of an hourj when the magnesia, if any exist, 

 will be precipitated Irom it, combined with carbonic 

 acid, and its quantity is to be ascertained in the 

 same manner as that of the carbonate of linie. 



If any minute proportion of alumina should, 

 from peculiar circumstances, be dissolved by the 

 acid, it will be found in the precipitate with the 

 carbonate of lime, and it may be separated from 

 it by boiling it (or a Jew minutes with soap lie, 

 sufficient to cover the solid matter : this substance 

 dissolves alumina, without acting upon carbonate 

 of lime. 



Should the finely-divided soil be sufficiently cal- 

 careous to effervesce very strongly with acids, a 

 very simple method may be adopted for ascertain- 

 ing the quantity of carbonate of lime, and one 

 sufficiently accurate in all common cases. 



Carbonate of lime, in all its states, contains a 

 determinate proportion of carbonic acid, /. e. near- 

 ly 43 per cent., so that when the quantity of this 

 elastic fluid given out by any soil during the solu- 

 tion of its calcareous matter in an acid is known, 

 ehher in weight or measure, the quantity of car- 

 bonate of lime may be easily discovered. 



When the process by diminution of weight is 

 employed, two parts ol' the acid and one part of 

 the matter of the soil must be weighed in two se- 

 parate bottles, and very slowly mixed together till 

 the effervescence ceases: the difference between 

 their weight before and affer the experiment de- 

 notes the quantity of carbonic acid lost ; lor every 

 four grains and a quarter of which, ten grains of 

 carbonate of lime must be estimated. 



The best method of collecting the carbonic acid, 

 so as to discover its volume, is by a peculiar pneu- 



* Fig. 15. A, B, C, D, represent the different parts 

 of this apparatus. A represents tlie bottle for receiv- 

 ing the soil. B the bottle containing the acid, fur- 



matic apparatus,* in which its bulk may be mea- 

 sured by the quantity of water it displaces. 



6. After the -calcareous parts of the soil have 

 been acted upon by nmriatic acid, the next process 

 is to ascertam the (juanlity of finely-divided inso- 

 uble animal and vegetable matter that it contains. 



This may be done with sufficient precision, by 

 strongly igniting it in a crucible over a common 

 fire till no blackness remains in the mass. It 

 should be often stirred wUh a metallic rod, so as to 

 expose new surfaces continually to the air; the loss 

 of weight that it undergoes denotes the quantity of 

 the substance that it contains destructible by fire 

 and air.* 



It is not possible, without very refined and dif- 

 ficult experiments, to ascertain whether this sub- 

 stance is wholly animal or vegetable matter, or a 

 mixture of both. When the smell emitted during 

 the incineration is similar to that of burnt feathers, 

 it is a certain indication of some substance either 

 animal or analogous to animal matter ; and a co- 

 pious blue flame at the time of ignition almost 



nisfied with a stop-cock. C the tube connected with 

 a flaccid bladder. D the graduated measure. E the 

 bottle for containing the bladder. When this instru- 

 ment is used, a given quantity of soil is introduced into 

 A. B is filled with muriatic acid diluted with an equal 

 quantity of water ; and the stop-cock being closed, is 

 connected with the upper orifice of A, which is ground 

 to receive it. The tube D is introduced into the lower 

 orifice of A, and the bladder connected with it placed 

 in its flaccid state into E, which is filled with water. 

 The graduated measure is placed under the tube of E. 

 When the stop-cock of B is turned, the acid flows into 

 A, and acts upon the soil ; the elastic fluid generated 

 passes through Cinto the bladder, and displaces a quan- 

 tity of water in E equal to it in bulk, and this water 

 flows through the tube into the graduated measure ; 

 and gives by its volume the indication of the propor- 

 tion of carbonic acid disengaged from the soil; for 

 every ounce measure of which two grains of carbonate 

 of lime may be estimated. 



* When the soil is aluminous, part of the loss in 

 the above process will be owing to water driven 

 off. Pure hydrate of alumina contains about 58 per 

 cent, water; the whole of which can only be expelled 

 by a white heat. On this accountthe ascertaining with 

 any accuracy the proportion of animal and vegetable 

 matter in a soil is difficult, and requires much chemi- 

 cal skill.— J. D. 



