SIR H. Davy's agricultural chemistry. 



Ill 



in diameter, will yield about 200 pints 

 of sap, and every 40 pints of sap afford 

 about a pound of sugar. The sap is neu- 

 tralized by lime, and deposits crystals of 

 sugar by evaporation. 



The sugar of grapes has been lately 

 employed in France as a substitute for 

 colonial sugar. It is procured from the 

 juice of ripe grapes by evaporation, and 

 the action of pot-ashes ; it is less sweet 

 than common sugar, and its taste is pe- 

 culiar : it produces a sensation of cold 

 while dissolving in the mouth ; and it is 

 probable contains a larger proportion of 

 water or its elements. The roots of the 

 beat (Beta vulgaris and cicla,) afford a 

 peculiar sugar, by boiling, and the evapo- 

 ration of the extract : it agrees in its ge- 

 neral properties with the sugar of grapes, 

 but has a slightly bitter taste. Manna, 

 a substance which exudes from various 

 trees, particularly from the Fraxinus or- 

 nus, a species of ash, which grows abun- 

 dantly in Sicily and Calabria, may be 

 regarded as a variety of sugar, very analo- 

 gous to manna ; it has been extracted by 

 Fourcroy and Vauquelin, from the juice 

 of the common onion, (Alium cepa.) 



Besides the crystallized and solid su- 

 gars, there appears to be a sugar which 

 cannot be separated from water, and 

 which exists only in a fluid form ; it con- 

 stitutes a principal part of molasses, or 

 treacle ; and it is found in a variety of 

 fruits : it is more soluble in alcohol than 

 solid sugar. 



The simplest mode of detecting sugar, 

 is that recommended by Margraaf. The 

 vegetable is to be boiled in a small quan- 

 tity of alcohol : solid sugar, if any exists, 

 will separate during the cooling of the 

 solution. Sugar has been extracted from 

 the following vegetable substances : — 

 The sap of the Birch (Betula alba,) of 

 the Sycamore (Acer pseudoplatanus,) the 

 Bamboo (Arundo bambos,) Maize (Zea 

 mays,) Cow Parsnip (Heracleum sphon- 

 dylium,) Cocoa nut tree (Cocos nucifera,) 

 Walnut tree (Juglans alba,) American 

 Aloe (Agave americana,) Dulse (Facus 

 palmatus,) Common Parsnip (Pastinica 

 sativa) St. John's bread (Ceratonia sili- 

 qua,) the fruit of the common Arbutus 

 (Arbutus unedo,) and other sweet tasted 

 fruits ; the roots of the Turnip, (Brassica 



papa,) of the Carrot (Daucus carota,) Pars- 

 ley, (Apium petroselinum,) the flower of 

 theEuxine, Rhododendron, (Rhododen-, 

 dron ponticum,) and from the nectarium 

 of most other flowers. 



The nutritive properties of sugar are 

 well known. Since the British market 

 has been overstocked with this article 

 from the West India Islands, proposals 

 have been made for applying it as the 

 food of cattle ; experiments have been 

 made which proved that they may be 

 fattened by it ; but difficulties connected 

 with the duties laid on sugar, have hith- 

 erto prevented the plan from being tried 

 to any extent. 



4. Jillmmen is a substance which has 

 only lately been discovered in the vege- 

 table kingdom. It abounds in the juice 

 of the papaw-tree, (Carica papaya :) when 

 this juice is boiled the albumen falls 

 down in a coagulated state. It is likewise 

 found in mushrooms, and in different spe- 

 cies of funguses. 



Albumen in its pure form is a thick, 

 glairy, tasteless fluid ; precisely the same 

 as the white of an egg ; it is soluble in 

 cold water; its solution, when not too di- 

 luted, is. coagulated by boiling, and the 

 albumen separates in the form of thin 

 flakes. Albumen is likewise coagulated 

 by acids and by alcohol : a solution of 

 albumen gives a precipitate when mixed 

 with a cold solution of nut-gall. Albumen 

 when burnt produces a smell of volatile 

 alkali, and affords carbonic acid and wa- 

 ter ; it is, therefore, evidently princi- 

 pally composed of carbon, hydrogen, 

 oxygen and azote. 



According to the experiments of Gay 

 Lussac and Thenard, 100 parts of albu- 

 men from the white of the egg are 

 composed of carbon 52.883 ; oxygen 

 23.872 ; hydrogen 7.540 ; azote 15.705. 

 This estimation would authorize the sup- 

 position that albumen is composed of 2 

 proportions of azote, 5 oxygen, 9 carbon, 

 23 hydrogen. The principal part of the 

 almond, and of the kernels of many other 

 nuts, appears from the experiments of 

 Proust, to be a substance analogous to co- 

 agulated albumen. 



The juice of the fruit of the Ochra (Hi- 

 biscus esculentus) according to Dr. Clark, 

 contains a liquid albumen in such quan- 



