S06 Drs. Will and Fresenius on the 



Method of Qiiantitative Ash-analysis. 



I. Preparatio7i of the Ash. — It is evident that the removal 

 of all foreign matter from the vegetable substances selected 

 is of the greatest importance: whether seeds, herbs or roots, 

 they should be carefully examined and freed from adherent 

 dirt before being bui'ned. They must not be washed, how- 

 ever, since in that case some of the soluble salts would be ex- 

 tracted; for the same reason, plants which have been exposed 

 in a withered or dead state, to rain or moist weather, should 

 not be employed. Plants in a healthy and natural condition 

 should always be selected, unless the object in view be the 

 study of disease and its causes. 



The information sought by means of ash-analysis, may have 

 reference to the quantity and quality of the inorganic matter 

 contained in a particular kind of plant, or part of a plant; or 

 it may be desired by its aid to judge of the properties of the 

 soil, as regards the presence in it of alkalies, alkaline earths 

 and phosphates. If the latter be the object, a quantitative ex- 

 amination of the ashes of all the plants grown upon the soil 

 will frequently suffice. A knowledge being once attained of 

 the composition of the ashes, both of the cultivated plants and 

 of the weeds, we shall be enabled to decide respecting the 

 composition of the soil, and its suitableness for the production 

 of each particular plant. 



Woods, herbs and roots, after being thoroughly dried, 

 should be burned upon a clean iron plate ; but for leaves, 

 fruits and seeds, it is more convenient to employ a hessian 

 crucible, heated by means of burning charcoal, in which it is 

 placed somewhat obliquely. The ash is occasionally very 

 easily burned white, but some seeds require a more elevated 

 temperature, to get rid of the charcoal which is intimately 

 mixed with the phos})hates ; care should always be taken, 

 however, to avoid heating so strongly as would cause the fu- 

 sion or softening of the alkaline salts, should they abound, or 

 it will be quite impossible to burn the charcoal, which in that 

 case becomes inclosed in the mass. It has properly been ob- 

 served by De Saussure, that the ashes are whitest when the 

 access of air has not been impeded by stirring or shaking 

 them together. 



The ash thus prepared should, if necessary, be further heated 

 to low redness in an open platinum capsule, over a spirit- 

 lamp, with constant stirring ; afterwards, and whilst still warm, 

 it should be rubbed to a very fine powder, intimately mixed, 

 and put into a well-closed bottle. 



It is now determined, by means of a qualitative analysis, to 

 which of the three groups the ash belongs. Its solubility in 

 concentrated hydrochloric acid is first ascertained : this is in 



