1838] 



FARMERS' REGISTER 



605 



nesia. They are procured by incineration. The 

 lime is usually conibiaecl with carbonic acid. This 

 substance anel silica, are much more commou in 

 the vegetable Iciuifdom than magnesia, ami mag- 

 nesia more common than alumina. The earths 

 form a principal |)art of the matter nisolnble in 

 water, atforded by the ashes of plants. The sili- 

 ca is known by not being dissolved by acids ; the 

 calcareous earth, unless the ashes have been very 

 intensely ignited, dissolves with clierveseence in 

 muriatic acid. Magnesia forms a soluble and 

 cryslallizable salt, and lime a difficultly soluble one 

 with sulphuric acid. Alumina is distinguished from 

 the other earths by being acted upon very slowly 

 by acids ; and in forming sails very soluble in 

 water, anddilBcult of crystallization with them. 



The earths appear to be compounds of the pe- 

 culiar metals before mentioned, and oxygen, one 

 proportion of each. 



The earths afforded by plants, are applied to no 

 uses of common life ; and there are li^AV cases in 

 which the knowledge of their nature can be of 

 importance, or afford interest to the fiirmer. 



The only metallic oxides found in plants, are 

 those of iron and manganesum : they are detect- 

 ed in the ashes of plants ; but in very minute 

 quantities only. When the ashes of plants are 

 reddish brown, they abound in oxides of iron. 

 When black or purple, in oxide of manganesum; 

 when these colours are mixed, they contain both 

 substances. 



The saline compounds contained in plants, or 

 afforded by their incineration, are very various. 

 The sulphuric acid combined with potassa, or sul- 

 phate of^ potassa, is one of the most usual. Com- 

 mon salt is likewise very often found in the ashes 

 of plants; likewise phosphate of lime, which is 

 insoluble in water, but soluble in nmriatic acid. 

 Compounds of the nitric, muriatic, sulphuric, and 

 phosphoric acids, with alkalies and earths, exist 

 in the sap of many plants, or are afforded by their 

 evaporation and incineration. The salts of potas- 

 sa are distinguished from those of soda by their 

 producing a precipitate in solutions of platina: 

 those of lime are characterized by the cloudiness 

 they occasion in solutions containing oxalic acid; 

 those of magnesia, by being rendered cloudy by 

 solutions of ammonia. Sulphuric acid is defected 

 in salts by the dense white precipitate it forms in 

 solutions of baryta. Muriatic acid by the cloudi- 

 ness it communicates to solution of nitrate of silver; 

 and when salts contain nitric acid, they produce 

 scintillations by being thrown upon burning coals. 



As no applications have been made of any of 

 the neutral salts or analogous compounds found in 

 plants, in a separate state, it will be useless to de- 

 scribe them individually. The following tables 

 are given from M. Th. de Saussure's Researches 

 on vegetation, and contain results obtained by 

 that philosopher. They exhibit the quantities of 

 soluble salts, metallic oxides, and earths afforded 

 by the ashes of different plants. 



Besides the principles, the nature of which has 

 been just discussed, others have been described 

 by chemists as belonging to the vegetable king- 

 dom: thus a substance, somewhat analogous ^0 

 the muscular fibre of animals, has been detected 

 by Vauquelin in ihe papaw; and a matter similar 

 to animal gelatine, by Braconnot, in the mush- 



room ; ulmin * and emetine, earcocol, nicotine, 

 olivile, asparagine, inulin, and other bodies, are 

 generally described in systetnatic writers on che- 

 mistry as specific compounds; but it is likely that 

 few of ihese bodies will retain their places as de- 

 finite combinations: their existence, likewise, is 

 extremely limited, and in this place it would be 

 improper to dwell upon peculiarities; my object 

 being to offer such general views of the constitu- 

 tion of vegetables as may be of" use to the agri- 

 culturist. It is probable, from the taste of sarco- 

 col, that it is gum combined with a little sugar. 

 Inulin is so analogous to starch, that it may be a 

 variety of that principle. If slight differences in 

 chemical and physical properties be considered as 

 sufficient to establish a difference in the species 

 of vegetable substances, the catalogue of them 

 might be enlarged to almost any extent. No two 

 compounds procured from different vegetables are 

 precisely alike ; and there are even differences in 

 the qualities of the same compound, according to 

 the time in which it has been collected, and the 

 manner in which it has been prepared. The 

 great use of classification in science is to assist the 

 memory, and it ought to be founded upon the 

 similarity of properties which are distinct, cha- 

 racteristic, and invariable. 



The analysis of any substance, containing mix- 

 tures of the different vegetable principles, may be 

 made, in such a manner as is necessary for the 

 views of the agriculturist, with facility. A given 

 quantity, say 200 grains, of the substance should 

 be powdered, made into a paste or mass, with a 

 small quantity of water, and kneaded in the hands, 

 or rubbed in a mortar for some time under cold 

 water: if it contain much gluten, that principle 

 will separate in a coherent mass. Afier this pro- 

 cess, whether it has afforded gluten or not, it 

 should be kept in contact with half a pint of cold 

 water for three or four hours, being occasionally 

 rubbed or agitated ; the solid matter should be se- 

 parated from the fluid by means of blotting paper. 

 The fluid should be gradually heated; if any 

 flakes appear, they are to be separated by the same 

 means as the solid matter in the last process, i. e. 

 by filtration. The fluid is then to be evaporated 

 to dryness. The matter obtained is to be exam- 

 ined by applying moist paper, tinged with red 

 cabbage juice, or violet juice, to it; if the paper 

 become red, it contains acid matter; if it become 

 green, alkaline matter; and the nature of the acid 

 or alkaline matter may be known by applying the 

 tests already described. If the solid matter be 

 sweet to the taste, it must be supposed to 

 contain sugar ; if bitterish, bitter principle, or 

 extract ; if astringent, tannin : and if it be nearly 

 insipid, it must be principally gum or mucilage. 

 To separate gum or mucilage from the other 

 principles, alcohol must be boiled upon the solid 

 matter, which will dissolve the sugar and the ex- 

 tract, and leave the mucilage; the weight of 

 which may be ascertained. 



* Ulmin, in relation to agricultural chemistry, would 

 appear, from the researches of M. BouUay, to be a 

 substance of some importance. It is of a dark colour, 

 almost black; nearly insoluble in water, having some 

 of the properties of an acid ; readily combining with al- 

 kalies and the alkaline earths, with which it forms so- 

 luble compounds. It is an ingredient of peat and ve- 

 getable mould, and may be considered as a natural 

 ' manure. — J. D. 



