ALK 



ALL 



hundred pair of plates, six inches square, 

 and one hundred and fifty pair, four inch- 

 es square, he has succeeded in decompo- 

 sing- potash and soda. A more brilliant 

 discovery has not been made since those 

 which have immortalized the names of 

 ley 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 

 disengaged, and the alkalies reduced to 

 their primitive base, which is found to be 

 a peculiar and highly inflammable mat- 

 ter, and which assumes the form and ap- 

 pearance of small globules of mercury. 

 These globules 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 mi- 

 croscope, they present a number of fa- 

 cettes with the appearance of crystalliza- 

 tion : at 40 Fahrenheit they are soft, 

 and can scarcely 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 atmosphere, they rapidly imbibe oxy- 

 gen, and reassume the alkaline charac- 

 ter. In distilled naptha they may be pre- 

 served four or five days, but if exposed 

 to the atmosphere, they almost instantly 

 become incrusted with a coat of alkali : 

 the incrustation may be removed, and the 

 reduced globule will remain, either in 

 naptha, or otherwise separated from all 

 contact with oxygen. See BITCMEX. 



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 en 

 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 



pan 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 oxydix.ement, all of which 

 it decomposed, seizing their oxygen, and 

 reassuming its alkaline qualities. From 

 many experiments it appears, that 1UO 

 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 constituent prin- 

 ciples of the earths barytes and stron- 

 tites. See CHKMISTBT, 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-vahed, 

 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 AI.LANTOJDES, in 

 comparative anatomv, a vesicle investing 

 the fetus of several animals, as cows, 

 sheep, goats, &c. and filled with aurinous 

 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, wliich 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 literal 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, wliich, 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 gay manner. 

 Allegros move swifter in triple than in 



