PYR 



PYR 



the Flint genus, its colour is dark blood 

 red, which, when held between the eye 

 and the light, falls strongly into yellow. 

 It occurs in angular grains, which are 

 imbedded, but never crystallized ; it is 

 completely transparent and hard; specific 

 gravity about 3.8. It is composed of 



Silica 40.00 



Alumina 28.50 



Magnesia 10.00 



Lime 3.50 



Oxide of iron 16.50 



manganese 0.25 



Loss 



98.75 

 1.25 



100 



It is found in many parts of Germany ; 

 also in Fifeshire in Scotland, in the sand 

 of the sea-shore. It is employed in almost 

 every kind of jewellery, and generally set 

 in gold foil. The very small grains are 

 powdered, and used in the stead of eme- 

 ry in cutting softer stones. This was for- 

 merly considered as a variety of the gar- 

 net, and denominated the Bohemian 

 Garnet, from its occurring in that country 

 in great beauty and perfection. Werner 

 has given the title to a distinct species, 

 on account of its colour, transparency, 

 and want of crystallization. 



PYROPHORUS, in chemistry, a com- 

 pound substance, which takes fire on the 

 admission of the atmospheric air. It is 

 prepared by exposing to heat in an iron 



Sot, three parts of alum, with one part of 

 our ; the mixture liquefies, and is to be 

 stirred constantly till the whole becomes 

 grey, and easily reducible to powder 

 while hot. 



The coarse powder is put into a coated 

 phial, so as nearly to fill it ; the mouth of 

 the phial is stopped with a small plug of 

 clay, and is placed in a crucible, and sur- 

 rounded with sand up to the neck. The 

 crucible is heated to redness, until a blue 

 flame appears at the mouth of the phial ; 

 when this has continued ten minutes, the 

 crucible is removed from the fire, and 

 the phial, when sufficiently cold, is accu- 

 rately stopped. This substance inflames 

 in atmospheric air; in a moist atmo- 

 sphere, the inflammation is much more 

 speedy, and in a dry air it can scarcely 

 take place. It burns also very brilliantly 

 in oxygen gas, in nitrous gas, and in oxy- 

 muriatic acid gas; and is inflamed by the 

 sulphuric and nitric acids. See ALUM. 

 PYUOSTRI A, in botany, a genus of the 



Tetrandria Monogynia class and order. 

 Natural order of Rubiacese, Jussieu. Ge- 

 neric character : calyx very small, four- 

 toothed; corolla be'll-shaped, five-cleft, 

 tomentose in the throat ; stamina four ; 

 pistils one ; stigma capitate ; pericarpium 

 drupe, pear shaped, inferior^ small, eight- 

 streaked; nuts eight, one-seeded. There 

 is but one species, viz. P. sulicifolia, a 

 native of the island of Mauritius. 



PYROTECHNY, is, properly speak- 

 ing, the science which teaches the ma- 

 nagement and application of fire in divers 

 operations ; but in a more limited sense, 

 and as it is commonly used, it refers 

 chiefly to the composition, structure, and 

 use of artificial fire-works. The ingredi- 

 ents are, 1. saltpetre, purified for the 

 purpose : 2. sulphur, and 3. charcoal. 

 Gunpowder is likewise used in the com- 

 position of fire-works, being first ground, 

 or, as it is technically termed, mealed. 

 Camphor and gum-benzoin are employed 

 as ingredients in odoriferous fire-works. 

 The proportions of the materials differ 

 very much in different fire-works, and 

 the utmost care and precaution are ne- 

 cessary in the working them to a state fit 

 for use, and then in the mixing. In this 

 work we cannot enter on the subject 

 with a sufficient degree of minuteness to 

 teach the method of making of fire-works, 

 and shall therefore content ourselves 

 with a brief notice of the proportions of 

 the materials in some of the more com- 

 mon, and more interesting articles in use. 



The charges for sky-rockets are made 

 of saltpetre, four pounds ; brimstone, one 

 pound ; and charcoal one pound and a 

 half; or by another direction, saltpetre, 

 four pounds ; brimstone, one pound and 

 a half; charcoal, twelve ounces; and 

 meal powder, two ounces. These pro- 

 portions vary again according to the size 

 of the rocket ; in rockets of four ounces, 

 mealed-powder, saltpetre, and charcoal, 

 are used in the proportions of 10 : 2 and 

 1 ; but in very large rockets the propor- 

 tions are, saltpetre, four ; mealed-powder 

 and sulphur, one each. When stars are 

 wanted, camphor, alcohol, antimony, and 

 other ingredients are required, accord- 

 ing as the stars are to be blue, white, &.c. 

 In some cases gold and silver rain is re- 

 quired ; then brass-dust, steel-dust, saw- 

 dust, &c. enter into the composition ; 

 hence the varieties may be almost in- 

 definite. With respect to colour, sulphur 

 gives a blue, camphor a white or pule 

 colour, saltpetre a clear white yellow, 

 sal-ammoniac a green, antimony a red- 

 dish, rosin a copper colour. These mu- 





