SALTS. 



stances (for instance, with the various sa- 1 

 line matters draining from a dunghill), that 

 then every difficulty is removed. Neither must 

 the cultivator suppose, that when saline sub- 

 stances are mixed with the soil, that then the 

 plant growing upon it absorbs those salts as a 

 matter of necessity, united with the moisture 

 contained in that soil, without having the power 

 of rejecting or separating it from its solution ; 

 for such an assumption has been proved to be 

 contrary to the fact by several \ r ery accural 

 experiments. M. Saussure, for instance, foun 

 that plants had the power, when placed in sa 

 line solutions, foreign to their habits, of seps 

 rating them from the water in which they wei 

 dissolved. These are researches fraught wit 

 instruction to the cultivator. He dissolved th 

 following salts in water, in such proportion 

 that each solution contained y^ part of it 

 weight of the salt muriate of potash, muriat 

 of soda (common salt), nitrate of lime, su 

 phate of soda (Glauber salt), muriate of air 

 monia (sal ammonia), acetate of lime, sulphat 

 of copper (blue vitriol). In each of these sc 

 lutions he put plants of Polygonum Persicn.ric 

 or of Bidcns cunnablna, furnished with thei 

 roots. The Polygonum grew for five weeks ii 

 the solution of muriate of potash, nitrate o 

 lime, muriate of soda, and sulphate of soda 

 and its roots increased in them as usual. I 

 languished in the solution of sal ammoniac 

 and the roots made no progress. It died in f 

 or 9 days in the solution of acetate of lime 

 and in less than 3 days in the solution of sul 

 phate of copper. When such a number ol 

 plants of Polygonum were put into the solu 

 tions as to absorb one-half of each in 2 days 

 the remaining half was found to have lost very 

 different proportions of the salt which it had 

 originally contained. Supposing the portion 

 of salt at first in solution to be 100, the follow- 

 ing table exhibits the quantity of each which 

 had disappeared when one-half of the liquid 

 was absorbed 



SALTS. 



6 C Nitrate of lime 

 ' 1 Sulphate of copper 



f Sulphate of soda - 

 7. -I Muriate of soda 



(.Acetate oflime 



Putt. 



n 



34 



6 

 10 







The Bidcns absorbed pretty nearly the same 

 proportions, but in general did not vegetate so 

 long as the Polygonum. 



When various salts were dissolved at once 

 in the same solution, and plants made to vege- 

 tate in them, it was found that different propor- 

 tions of the salts were absorbed. The follow- 

 ing table exhibits the results of these trials, 

 supposing, as before, the original weight of 

 each salt to have been 100, each solution con- 

 tained T 6 part of its weight of each salt 



, f Sulphate of soda - 

 ' \ Muriate of soda 

 o f Sulphate of soda - 

 ' \ Muriate of potash - 

 o S Nitrate of lime 



(.Muriate of ammonia 

 4 f Acetate oflime 

 * 1 Sulphate of copper 

 . f Acetate of lime 

 (Muriate of potwb - 

 974 



Part*. 

 11-7 

 22 

 12 

 17 

 4-5 

 166 

 31 

 34 



8 



17 



These experiments succeeded nearly equally 

 with other plants, as the Mentha piperita and 

 the Scotch fir. When the roots were cut or 

 removed, the plants absorbed all solutions in- 

 discriminately; on examining the plants, the 

 salts absorbed were found in them unaltered. 

 It being thus clearly established that plants 

 possess a discriminating power, and that they 

 do not absorb saline solutions merely because 

 they happen to be dissolved in the soil, it next 

 becomes an object of interest, as an illustra- 

 tion and guide for the operations of agricul- 

 ture, to ascertain what salts are found by the 

 researches of the chemist in commonly culti- 

 vated plants. And if, at the conclusion of our 

 examination, we find that certain salts are 

 found in abundance only in certain plants, and 

 that these saline substances exist in them in- 

 variably in all soils and situations, and that 

 without their presence the plant languishes and 

 merely supports a sickly existence, we shall 

 be almost driven to the conclusion, that these 

 are as essentially the food of plants, as any of 

 the other substances with which they abound. 



For a lengthened period, the vegetable alka- 

 kne salt, carbonate of potash, has been ob- 

 tained from plants. Procured at first by their 

 combustion, in iron pots, it hence obtained its 

 name. Dr. Thomson has given a table of the 

 quantity of potash obtained from 100 parts of 

 the ashes of various trees and plants. See 

 ALKALI. 



In general, says Dr. Thomson, three times as 

 much ashes are obtained from shrubs as from 

 ,rees. An equal weight of the branches of 

 rees produce more ashes than the trunk, and 

 he leaves more than the branches. Herbs ar- 

 rived at maturity produce more ashes than at 

 any other time. Green vegetables produce 

 more ashes than dry. The salt which is ob- 

 ained by the combustion of plants, although 

 hiefly composed, does not consist wholly of 

 >otash: there are many salts mixed with it;, 

 hese are usually sulphate of potash, muriate 

 3f potash, sulphate of lime, phosphate of lime, 

 &c., but these bear in general but a small pro- 

 ortion to the potash. 



Perhaps the most copious table of the alka- 

 ine and other salts obtained by the combus- 

 ion of various plants has been given by M. 

 Saussure in his chemical researches on'vege- 

 ation. He obtained from 100 parts of the 

 shes of the 



Leaves of oak (Querciw Robtir), May 10 'J? 



Do., September 27 - . 17- 



Wood of a young oak, May 10 7- 



Bark of do. ---.._ 7. 



Perfect wood of oak - ... 39^5 



Albumen of do. 32- 



Bark of do. 7. 



Cortical layers of do. - -' _ 7. 



Extract of wood of do. - - - - 51- 



Soil from the wood of do. 84- 



Extract from do. (yj. 



Leaves of poplar (Popnlut nigrci), May 10 36- 



Do., September 12 - . _ . 28- 



Leaves of hazel 28- 



Do., washed in cold water ... 8-2 



Leaves of do., June 22 .... 82-7 



Do., September 2 - - - - 11- 



