1837] 



FARMERS' REGISTER. 



279 



water; Thcnaril, that feciila combines easily with 

 boiiinsi-watrr. lorn)in<T a hydrate popularly termed 

 ptarch; and l)e?pretz, tiiat, when tecuki is mi\ed 

 wiiii l)oiliiiix-\vater, it hcconies soluble, and does 

 not recover its in^:o!llbilty in cold water, when eva- 

 porated to dryness, — ihey all speak vairuely, and 

 in par' incorrectly, from not knowing llio discov- 

 ery of Raspail already mentioned. The kernel 

 contained in the<i!obular envelope of fecula, con- 

 sists ol" a iTum-like matter, which, by the evapo- 

 ration of its watery parts, becomes hard on expo- 

 sure to the air. When immersed in water at 

 122°, the envelope, whicii is unaffected by colder 

 water, expands, and in builintr-water it burslf, 

 while the kernel is dissolved in the water. — 

 When the water is in largp, quaulity, the envel- 

 opes detached from their kernels, and now ten 

 limes their oriirinal size, havinfj free motion, sub- 

 side; but when ^he quantity of wafer is .small, 

 they become mutually entansjled, Ibrm jelly-like 

 strata or layers, and render the water thick, — 

 bein<T what is termed starch in the laundry (em- 

 pois). 



M. Raspail, from numerous experiments, con- 

 cludes, that eacli jirain of feculn is an organized 

 globule, formed in the interior of livinij vegetable 

 cells, such as in those of a grain of" wheat, or of 

 the tuber of a potato; that the enveloping mem- 

 brane of the kernel is incapable of being dissolv- 

 ed in cold water, spirits of wine, ether, or the 

 acids, but expanding in proportion 'o the decree of 

 heat, and in boilins:- water burs!in<r on one side of 

 the globule; and that after boilintj in a large quan- 

 tity of water, the burst and detached envelopes 

 f;\ll to the oottom in the form of snow-whi'e 

 flakes, leaving the liquid above them as limpid as 

 water. 



"Wiih respect to the kernel contained within the 

 evelopes, M. Raspail concfudes. that if the limpid 

 liquid be cautiously poured off. the addition of 

 spirits of wine, the concentrated acids, or tincture of 

 galls will coagulate it, but will not coagulate by 

 heal; that it acquires a blue color by addinir iodine, 

 a property it possesses in common with the enve- 

 lopes, but it loses this property by beinir spread out 

 thinly on a porcelain plate and dried, differing in 

 that case in no respect from ffum: and that it does 

 not lose its characters on being dried by a mode- 

 rate heat, which causes it more to resemble oum 

 with a glass-like fracture, a splintery texture, and 

 a shining surliice. 



We have M. Raspail's authority, then, for con- 

 sidering the kernel within the envelopes in starch 

 as resembling srum, if not identical with it in phys- 

 ical and chemical characters, and hence we 

 mitrht be led to believe that the nutritive or soluble 

 part is ffum, or of the nature of gum. At thisstatze 

 of the inquiry, however, M. Biof, along with M. 

 Persoz, took up the subject, and succeeded so far 

 in discovering a distinct and very remarkable dif- 

 ference from gum. Accordingly, on isolating the 

 kernel portion of the parsnip'root, by boiling to 

 burst the envelopes, precipitating bv alcohol, pu- 

 rityin? by repeated washinjis with alcohol, and 

 then dissolving it in water in order to observe in 

 what manner it polarized light, it was found that 

 it turned the planes of polarization with more en- 

 ergy towards the riirht than any substance yet 

 known; while all xrums, and the sufrar of grapes, 

 turn the planes of polarization towards the left. 

 Cane sugar, indeed, turns the planes of polariza- 



tion towards the right, but not with the same en- 

 ergy as the kernels of starch. 'J'he latter, there- 

 liire, IMIVI. niotand Persnz term dc.iirinc, and we 

 shall adopt the term, notwilhsiandinix Al. Ras- 

 pail objects to it, till one more appropriate be |)ro- 

 [losed. The soluble portion accordingly of starch, 

 or the fiirinaceo IS matter of grain and rnuts, is 

 dextrine, which is always contained in a globular 

 envelope, composed of membranes that are inca- 

 pable of being dissolved in water even when 

 boiling. By means oftliis singular and unex[)ect- 

 ed test of turning the planes of polarization to- 

 wards the right of the observer, the nutritive 

 (]ualities of all vegetable substances can be exam- 

 ined, and many of them have been so examined 

 by M. Biot, as we shall presently see. Amongst 

 other vegetable productions, JM. Biot examined 

 the juice of the carroty taken from the white vari- 

 ety, by cold pressure. He dividetl this into two 

 parts, one part being filtered through white paper 

 without being heated; and another, alter being 

 similarly filtered, was brought for an instant to 

 the boiling point. Tlie result was most impor- 

 tant in a practical point of view; the part wfiich 

 had been brought to a boiling temperature pro- 

 duced a rotation towards the right exactly double, 

 of that which had not been heated', and its abso- 

 lute intensity corresponded to the proportion of 

 four per cent, of cane-sugar, asded^uced from pre- 

 vious observation. 



"The li(]uor," continues JVl. Biot, "treated with 

 alcoliol, gave a considerable precipitate,, which 

 was instantly re-dissolved in water, as the case 

 with dextrine, and this appears to me to explain 

 sutRciently the sudden increase of the rotation af- 

 ter the boiling." It will fi^llow that even a slight 

 boiling doubles the nutritive quality of carrots, a 

 fiict known indeed from other experiments but 

 only in a vague manner, without any philosophi- 

 cal data to explain it by. 



The juice of the turnip exhibited similar pheno- 

 mena. When it was procured by sini[)le pressure 

 and filtered through paper, the portion which 

 passed the filler exercised no rotation that could 

 be appreciated; but on boilina it with tiie pulp a 

 liquid was obtained, which turned the planes of 

 polarization towards the right, indicating cane- 

 sugar, as found in llie turnip by chemical ana- 

 lysis. 



In the juice of the beet-root; so interesting on 

 account of the increasing manufacture of sugar 

 from it, M. Pelouze, a young, but able chemist, 

 having found no grape-sugar,, or such as is inca- 

 pable of crystallization, and only crystallizable 

 sugar, M. Biot undertook experiments to investi- 

 gate the subject still farther. Taking the fresh 

 juice of. the beet-root, he repeatedly measured 

 with the greatest care the intensity of rotation 

 which it communicated to polarized light,, which he 

 found to vary from 10° to 12'' 6', according to the 

 ditference of individual roo's, or different parts of 

 the same root, indicating from 11 to 14 per cent, 

 of cane-sugar. The crown and the sides of the 

 root being less mature than the centre, appeared 

 to him to be less rich in the proportion of nine to 

 ten. As the beet-root on which the experiments 

 w-ere made had been taken from a field very libe- 

 rally manured, the larjie proportion of saccharine 

 matter, indicated by the intensi'y of the rotation, 

 confirmed the remark ofM. Pelouze that the rich- 

 ness of the manure did not diminish the constitu- 



