no 



SIR H. DAVY S AGRICULTURAL CHEMISTRY, 



Supposing this estimation correct,starch 

 may be conceived to be constituted by 15 

 proportions of carbon, 13 of oxygen, and 

 26 of hydrogen. 



Starch forms a principal part of a 

 number of esculent vegetable substances. 

 Sovvans, cassava, salop, sago, all of ihem 

 owe their nutritive powers principally to 

 the starch they contain. 



Starch has been found in the following 

 plants : 



Burdock (Arctium lappa,) Deadly 

 Nightshade (Atropa belladonna.) Bistort 

 (Polygonum bistorta,) White Bryony 

 (Bryonia alba,) Meadow Saffron (Colchi- 

 cum autuninalc,) Dropwort (Spirea lil- 

 ipendula,) Buttercup (Ranunculus bulb- 

 osos,) Figwort (Scrophularia nodosa,) 

 Dwarf Elder (Sambucus ebulus,) Com- 

 mon Elder (Sambucus nigra,) Foolstones 

 (Orchis morio,) Alexanders (Imperatorio 

 ostruthium,) Henbane (Hyoscyamus ni- 

 ger,) Broad-leaved dock (Rumexobtusifo- 

 lius,) Sharp pointed Dock(Rumex acutus,) 

 Water Dock (Rumex aquaticus,) Wake 

 Robin (Arum raaculatum,) Salop (Orchis 

 mascula,) Fleur de luce or Water Flag, 

 (Iris pseudocorous,) Stinking Gladwyn 

 (Iris foetidissima,) Earth Nut (Bunium 

 bulboeastanum.) 



3. Sugar in its purest state is prepar- 

 ed from the expressed juice of the Sac- 

 charum officinarum, or sugar cane ; the 

 acid in this juice is neutralized by lime, 

 and the sugar is crystallized by the evapo- 

 ration of the aqueous parts of the juice, 

 and slow cooling : it is rendered white 

 by the gradual filtration of water through 

 it. In the common process of manufac- 

 ture, the whitening or refining of sugar 

 is only affected in a great length of time : 

 the water being gradually suffered to per- 

 colate through a stratum of clay above 

 the sugar. As the coloring matter of 

 sugar is soluble in a saturated solution of 

 sugar, or syrup, it appears that refining 

 may be much more rapidly and economi- 

 cally performed by the action of syrup of 

 colored sugar.* The sensible properties 



* A French gentleman lately in this country (Eng- 

 land) stated to the West India planters that he was in 

 possession of a very expeditious and economical me- 

 thod of purifying and refining, which he was willing 

 to communicate to them for a very groat pecuniary com- 

 pensation. His terms were too high to be acceded 



of sugar are well known. Its specific 

 gravity, according to Fahrenheit, is about 

 1.6. It is soluble in its own weight of 

 water at 50° ; it is likewise soluble in al- 

 cohol, but in smaller proportions. 



Lavoisier concluded from his experi- 

 ments, that sugar consists in 100 parts 

 of— 



2S carbon, 

 8 hydrogen, 

 64 oxygen. 

 Dr. Thomson considers 100 parts of 

 sugar is composed of — 

 27.5 carbon, 



7 S hydrogen, 

 64.7 oxygen. 

 According to recent experiments of 

 Gay Lussac and Thenard, sugar consists 

 of— 



42.47 of carbon, and 

 57.53 of water, or its elements. 

 Lavoisier's and Dr. Thomson's .analy- 

 ses agree very nearly with the propor- 

 tions of — 



3 of carbon, 



4 of oxygen, 



8 of hj^drogen. 



Gay Lussac's and Thenard's estima- 

 tion gives the same elements as in gum : 

 11 of carbon, 10 of oxygen, 20 of hydro- 

 gen. 



It appears from the experiments of 

 Proust, Achard, Goettling and Parmen- 

 tier, that there are many different species 

 of sugar ready formed in the vegetable 

 kingdom. The sugar which most nearly 

 resembles that of the cane, is extracted 

 from the sap of the American Maple, 

 Jicer saccharinum. This sugar is used 

 by the North American farmers, who pro- 

 cured it by a kind of domestic manufac- 

 ture. The trunk of the tree is bored 

 early in the spring, to the depth of about 

 two inches ; a wooden spout is introduced 

 into the hole ; the juice flows for about 

 five or six weeks. A common sized 

 tree, that is, a tree from two to three feet 



to. Conversing on the subject with Sir John Banks, 

 I mentioned to him, that I thought it probable that 

 raw sugar might be easily purified by passing syrup 

 through it, which would dissolve the coloring matter. 

 The same idea seems to have occurred about the same 

 time, or before, to Edward Howard, Esq., who has 

 since proved its efficacy experimentally, and has pub- 

 lished an account of his process. 



