192 Bibliography. 



"The amount of vegetable matter soluble in a solution of carbon- 

 ate of ammonia, is 1.25 grains, and a solution of carbonate of potash 

 takes up 1.8 grains. 



" The vegetable soluble matters analyzed, were ascertained to be 

 the crenic and apocrenic acids, with a little crenate of lime." 



We would add, that the method by which this analysis was per- 

 formed, seems defective in not testing for the presence of carbonic 

 acid in the soil before heating to full redness, whereby, in all proba- 

 bility, the carbonic acid is expelled ; for we have since obtained sat- 

 isfactory proof of the existence of carbonic acid in the Nile soil.* 

 This soil was judged to contain no potassa on the evidence yielded 

 by the trial prescribed in the present plan of analysis, (by diges- 

 tion with nitric acid and deflagration with charcoal.) But Professor 

 Mitscherlich has shown that the existence of potassa in aluminous 

 soils may be much more satisfactorily proved by digesting them with 

 sulphuric acid, when if any potash is present alum will be found. 

 We accordingly digested 200 grains of Nile soil in dilute sulphuric 

 acid, filtered it, and evaporated the solution to entire dryness, redis- 

 solved in distilled water, and on concentrating the solution, (which 

 had a very strong taste of alum,) obtained distinct crystals of sul- 

 phate of alumina and potassa. This result is satisfactory, inasmuch 

 as it makes the analysis coincide more nearly with those which have 

 been before published from the same country, all of which represent 

 the soil as containing potash. 



The method pursued in estimating the organic constituents of soils, 

 was different from that which has been generally followed in similar 

 cases, and entitled to much confidence. So far as we are informed. Dr. 

 Jackson is the first who has proved by reiterated trials, that the so 

 called humus, geine, apotheme, &lc. of previous authors, is mainly 

 composed of two acids, first discovered by Berzeliusf in the waters of 

 Porla Well, in Sweden, and called by him (from i(Q-)]vr], a fountain) 

 crenic and apocrenic acids. They communicate to that water a bitter 

 taste and slightly brown color, and have been fully described by him 

 in the memoir before the Stockholm Academy in 1833, before cited. 

 We cannot here give any account of the properties of these acids, 

 nor is it necessary, since their history may be found detailed in the 

 standard works. (See Thomson's Chemistry of Organic Bodies, 

 Vegetables, 1838, p. 153 et seq.) 



Whoever will read with attention the profound work of M. Liebig, 

 noticed in this number, will feel, if his conclusions are to become the 



* Consequently the 2.02 of phosphate of lime in the above analysis, would pro- 

 bably be nearer the truth if it read carbonate instead of phosphate of lime, 

 t L. c. p. 178. 



