ALK 



ALL 



hundred pair of plates, six inches square, 

 and one hundred and fifty pair, four inch- 

 es square, he has succeeded in decompos- 

 ing potash and soda. A more brilliant 

 discovery has not been made since those 

 which have immortalized the names of 

 Priestley and Cavendish. This was ef- 

 fected by placing moistened potash, or 

 soda, on a plate of platina, and exposing 

 it to the galvanic circle. Oxygen was dis- 

 engaged, and the alkalies reduced to their 

 primitive base, which is found to be a pe- 

 culiar and highly inflammable matter, and 

 which assumes the form and appearance 

 of small globules of mercury. These glo- 

 g-ules are, however, lighter than water, 

 and when potash is used, they are in the 

 proportion of 6 to 10. At the freezing 

 point they are hard and brittle ; and when 

 broken and examined by a microscope, 

 they present a number of facettes, with 

 the appearance of crystallization : at 40 

 Fahrenheit they are soft, and can scarce- 

 ly be discriminated but by their gravity 

 from globules of mercury ; at 60 they 

 are fluid, and at the small heat of 100 

 volatile. When exposed to the atmo- 

 sphere, they rapidly imbibe oxygen, and 

 reassume the alkaline character. In dis- 

 tilled naptha they may be preserved four 

 or five days, but if ex'posed to the atmo- 

 sphere, they almost instantly become in- 

 crusted with a coat of alkali : the incrus- 

 tation may be removed, and the reduced 

 globule will remain, either in naptha, or 

 otherwise separated from all contact with 

 oxygen. See BITUMEN. 



One part of the base of alkali and two 

 of mercury, estimated by bulk, form an 

 amalgam, which, when applied in the cir- 

 cle of a galvanic battery, producing an 

 intense heat to iron, silver, gold, or pla- 

 tina, immediately dissolved them, and 

 converted them into oxides, in which pro- 

 cess alkali was regenerated. Glass, as 

 well as all other metallic bodies, was also 

 dissolved by the application of this sub- 

 stance : the base of the alkali seizing the 

 oxygen of the manganese and of the mi- 

 nium, potash was regenerated. One of 

 these globules placed on a piece of ice 

 dissolved it, and burnt with a bright 

 flame, giving out an intense heat. Potash 

 was found in the product of the dissolved 

 ice. Nearly the same effects followed, 

 when a globule was thrown into water : 

 in both cases a great quantity of hydro- 

 gen was rapidly liberated. When laid on 

 a piece of moistened turmeric paper, the 

 globule seemed instantly to acquire an in- 

 tense heat ; but so rapid was its move- 

 ment in quest of the moisture, that no 



part of the paper was burnt, only an in- 

 tense deep red stain marked the course it 

 followed, and showed a reproduction of 

 alkali. The specific gravity of the base 

 of soda is as seven to ten of water: it is 

 fixed in a temperature of about 150, and 

 fluid at 180. Mr. Davy next tried its 

 effects on the phosphates, phosphurets, 

 and many other salts of the first and se- 

 cond degree of oxydizement, all of which 

 it decomposed, seizing their oxygen, and 

 reassuming its alkaline qualities. From 

 many experiments it appears, that 100 

 parts of potash contain 15 of oxygen, and 

 85 of an inflammable base, and that the 

 same quantity of soda contains 20 of oxy- 

 gen, and 80 base. This ingenious chemist, 

 after a great number of complex experi- 

 ments, in which he was assisted by Messrs. 

 Pepys and Allen, ascertained that oxygen 

 is also an essential ingredient in ammo- 

 nia; of which 100 grains appeared to 

 yield 20 of oxygen. Mr. Davy has also 

 found that oxygen is one of the constitu- 

 ent principles of the earths barytes and 

 strontites. See CHEMISTRY, POTASH, and 

 SODA. 



ALLAMANDA, in botany, a genus of 

 the Pentandria Monogynia class and or- 

 der : corolla twisted ; capsule, lens-form, 

 erect, echinate, one-celled, two-valved, 

 many-seeded. One species, viz. catharti- 

 ca, a climbing plant, found in Guiana, near 

 rivers. The infusion of its leaves is used 

 in the cholic. 



ALLANTOIS, or ALLANTOIDES, in com- 

 parative anatomy, a vesicle investing the 

 fostus of several animals, as cows, sheep, 

 goats, &c. and filled with a urinous liquor 

 conveyed thither from the urachus. 



ALLEGIANCE, is the lawful duty from 

 the subject to the sovereign ; and is either 

 natural, as every subject born ought to 

 pay ; acquired, where a man is naturaliz- 

 ed ; local, which a man ought to pay who 

 comes under the dominion of the king. 



ALLEGORY, in matters of literature, 

 a mode or species of writing, wherein 

 something else is signified than the words 

 in their l : teral meaning express. An al- 

 legory may be considered as a series or 

 chain of metaphors, continued through a 

 whole discourse For example, when the 

 prophets represent the Jews under the 

 allegory of a vine, planted, cultivated, and 

 watered, by the hand of God, which, in- 

 stead of producing good fruit, brings 

 forth verjuice and sour grapes. 



ALLEGRO, in music, an Italian word, 

 denoting that the part is to be played in 

 a sprightly, brisk, lively, and guv manner. 

 AUegroes move swifter in triple than in 



