PHO 



The object may be improved with re- 

 spect to the production and propagation 

 of sounds. With regard to the medium, 

 phonics may be improved by its thinness 

 and quiescency, and by the sonorous bo- 

 dy being placed near a smooth wall, 

 either plain or arched, more especially 

 if it be formed after some peculiar curve, 

 as from this arises the theory and prac- 

 tice of whispering places. Sound is much 

 sweetened if it is propagated in the vicini- 

 ty of water ; arid on a plain, itwill be con- 

 veyed much further than on uneven 

 ground. 



FHORMIUM, in botany, a genus of the 

 Hexandria Monogynia class and order. 

 Natural order of Coronarise. Asphodeli, 

 Jussieu. Essential character : calyx none ; 

 corolla six-petalled, the three inner petals 

 longer; capsule oblong, three- sided ; 

 seeds oblong, compressed. There is but 

 one species, viz. P. tenax, New Zealand 

 flax-plant. The inhabitants of New Zea- 

 land make a thread of the leaves, with 

 which the women weave a variety of fine 

 matting for clothing, and several other 

 purposes. It is also manufactured in Nor- 

 folk Island for canvass and coarse linen 

 cloths. 



PHOSPHATES, in chemistry, salts 

 formed of the phosphoric acid, with 

 earths, alkalies, &c. The alkaline phos- 

 phates are soluble and crystallizable ; 

 they are also fusible, forming a kind of 

 glass, and facilitate the fusion of a num- 

 ber of other substances. They may be 

 decomposed in the humid way, by sul- 

 phuric and some other acids ; but in 

 the dry way these decompositions do 

 not often happen. The phosphate of so- 

 da is much used in medicine ; it is pure- 

 ly saline, without any bitterness, which 

 renders it a good substitute for Epsom 

 and Glauber's salts. As it melts easily, 

 and promotes the fusion of the earths 

 and metallic oxides, it is used in che- 

 mical operations as a flux. Phosphate 

 of ammonia exists in the urine of car- 

 nivorous animals, in considerable quan- 

 tity, united with phosphate of soda, 

 forming a triple salt, formerly denomi- 

 nated microcosmic, or fusible salt, in 

 urine. 



PHOSPHITES, are salts formed of the 

 phosphorous acid, with alkalies, earths, 

 &c. In several of their properties they 

 resemble the phosphates; but may be 

 distinguished from them, by appearing 

 luminous when heated with the blow- 

 pipe, and by affording, by distillation, a 

 small quantity of phosphorus. They de- 

 tonate, too, with oxy-muriate of potash, 



and precipitate gold from its solution in 

 a metallic state. By exposure to the air, 

 they pass into phosphates. 



PHOSPHORESCENCE, 7 e T 

 PHOSPHOR!, 5 See LlGHT - 



PHOSPHORIC acid. When phospho* 

 rus undergoes combustion in oxygen gas, 

 a great quantity of white fumes are pro- 

 duced, which are deposited in white 

 flakes. These are phosphoric acid ; so 

 that it is a compound of phosphorus and 

 oxygen. The phosphoric acid was first 

 shewn to be distinct from all other acids, 

 in the year 1743, by Margraaflf. He found 

 that it existed in the salts which were 

 taken from human urine, and that phos- 

 phorus could only be obtained from 

 this acid ; as well as that it could be con- 

 verted into phosphoric acid. This acid 

 was found to exist in some vegetable sub- 

 stances, although it was formerly suppos- 

 ed to be peculiar to animal matters. 

 Phosphoric acid may be obtained, not on 

 ly by the method just mentioned, but also 

 by transmitting a current of oxygen gas 

 through phosphorus melted under water. 

 The acid, as it is formed, combines with 

 the water, from which it may be obtained 

 in a state of purity by evaporation. The 

 specific gravity of this acid varies accord- 

 ing to the different states in which it ex- 

 ists. In the liquid state it is 1.4 ; in the 

 dry state it is 2.7 ; in the state of glass 

 2.85. It changes the colour of vegetable 

 blues to red ; has no smell, but a very 

 acid taste. When it is exposed to the 

 air it attracts moisture, and is converted 

 into a thick viscid fluid, like oil. It is very 

 soluble in water. When in the form of 

 dry flakes, it dissolves in a small quantity 

 of this liquid, producing a hissing noise 

 like that of a red-hot iron plunged into 

 water, with the extrication of a great 

 quantity of heat. The component parts 

 of this acid have been accurately as- 

 certained by Lavoisier, and it consists 

 of, 



Oxygen 60 



Phosphorus 40 



100 



It combines with the alkalies, earths, 

 and metallic oxides, and forms salts which 

 are denominated phosphates. 



PHOSPHORITE, in mineralogy, is of 

 a yellowish white, frequently spotted vyith 

 grey : it occurs massive ; internally it is 

 glistening, sometimes dull; it is trans- 

 lucent on the edges, soft, brittle, and not 



