886 



WATER. 



of eminence on the fine arts and the belles-lettres. 

 He held the office of a receiver-general of the 

 finances, was a member of the French academy, 

 and of several foreign learned societies, and died 

 at Paris, in 1786, aged sixty-eight. He published, 

 in 1760, a poem Sur I' Art de peindre, and was the 

 author of several other works, the most important 

 of which is the Dictionary of Painting, Sculpture 

 and Engraving, forming part of the Encyclopedic 

 Afethodique. 



WATER. The composition of this fluid has 

 been fully demonstrated both from analysis and 

 synthesis. It is found that when hydrogen gas is 

 burnt (an operation in which oxygen is combined 

 with it), water is formed, and is the only sensible 

 product. This is the proof by synthesis. On the 

 other hand, when water is acted on by substances 

 capable of attracting oxygen, these are oxidated, the 

 water disappears, and hydrogen gas is evolved. 

 The proportions of these elements in water are as 

 follows : one volume of oxygen to two volumes of 

 hydrogen ; or, by weight, eight parts oxygen to one 

 of hydrogen. Water is a transparent and colour- 

 less liquid, destitute of smell, and nearly without 

 taste. It refracts light powerfully. When its in- 

 ternal movements are prevented, it is a very slow 

 conductor of heat, and an imperfect conductor of 

 electricity. It is almost incompressible, a pres- 

 sure equal to 2000 atmospheres occasioning a 

 diminution of only one ninth of its bulk. Water 

 being the substance most easily procured in every 

 part of the earth in a state of purity, it has been 

 chosen, by universal consent, to represent the unit 

 of the specific gravity of all solid and liquid bodies. 

 When we say the specific gravity of a body is two, 

 we mean that it weighs twice as much as the same 

 volume of water would do. Now, a cubic foot of 

 water, at the temperature of 60 Fahr., and when 

 the barometer stands at 30 inches, weighs 998-217 

 avoirdupois ounces, which is only 1 -783 ounces less 

 than 1000. Hence, if we know the specific gravity 

 of a body, we have very nearly the weight of a 

 cubic foot of it in avoirdupois ounces. 100 cubic 

 inches of air at 60 Fahr., when the barometer 

 stands at 30 inches, weigh 31-1446 grains. Hence 

 it follows that water, at that temperature and pres- 

 sure, is 810-734 times heavier than air. Water 

 passes to the solid state at 32 Fahr. When it 

 shoots into ice, it forms, in the first place, a prism, 

 not very regular in shape, but very long. From 

 this primary prism other smaller ones shoot out on 

 both sides, and always at angles of 60 and 120. 

 Hail is always crystallized in the form of two six- 

 sided pyramids applied base to base. Ice has been 

 observed in crystals having the form of a rhomboid 

 of 120 and 60. In taking the solid form, water 

 undergoes an enlargement of volume from eight 

 parts to nine ; and this expansion even takes place 

 previous to the congelation, during the reduction 

 of temperature for six or eight degrees, the great- 

 est density of water being about 40 Fahr. In the 

 act of freezing, too, the greater part of the air, 

 which the water holds loosely dissolved, is expelled. 

 Electricity is also rendered sensible in its congela- 

 tion. Water passes into vapour when exposed to 

 the atmosphere at any natural temperature, and 

 even ice evaporates, as is proved by its losing 

 weight when suspended in the air. The transition 

 into vapour is promoted by heat: at 212, under a 

 medium atmospheric pressure, water boils.. (See 

 Steam.) Water absorbs the aerial fluids, but in 

 quantities very different, according to the force of 



attraction which it exerts towards them. Of fome 

 of the acid gases it absorbs many times its own 

 volume ; of others, the quantity is so inconsidoiii- 

 ble as not to be very perceptible, unless ascertained 

 by an apparatus peculiarly adapted to show the re- 

 sult. The quantities absorbed are greater as the 

 temperature is low, down to freezing. They are 

 also augmented by pressure. 100 cubic inches of 

 recently-boiled water, at the mean temperature and 

 pressure, absorb of 



Sulphureted hydrogen, 100 cubic inches. 



Carbonic arid 100 



Nitrous oxide, 10f> 



Olefiant gas, 12-5 



Oxygen, 3-7 



Carbonic oxide, 1'56 



Nitrogen, 1-66 



Hydrogen, 1-86 



All water which has been exposed to the at- 

 mosphere (as spring and river water) contains a 

 portion of air, from which it derives a sparkling 

 quality and agreeable taste. It is thus also fitted 

 for supporting the respiration of fishes. It appears 

 that the oxygen is absorbed in preference to the 

 nitrogen, and in considerably larger quantity. All 

 the powerful acids exert a strong attraction for 

 water, such as the sulphuric, the nitric, muriatic, 

 fluoric and phosphoric acids. Few of these can 

 even be obtained free from it in an insulated state ; 

 and it appears to have an important effect in their 

 more characteristic acid properties. A strong at- 

 traction is exerted between water and the fixed al- 

 kalies, as also between it and the alkaline earths. 

 The compound salts, also, always contain water, 

 even those of them which appear altogether insolu- 

 ble. Water, though incapable of combining with 

 the metals, exerts a chemical action upon them, af- 

 fording to several of them oxygen, at the tempera- 

 ture of ignition, and, at a natural temperature, 

 aided by atmospheric air, oxidating or corroding 

 others : it also combines with some of their oxides. 

 Water is a solvent of many other substances. Few 

 of the animal or vegetable products are insoluble in 

 it, and all of them are affected by it as a chemical 

 agent. Those compounds in which water exists in 

 intimate combination, and the properties of which 

 it appears to modify, are named hydrates. It some- 

 times exists in union, in the proportion of one atom 

 (represented by nine to hydrogen as one) ; some- 

 times two atoms (or eighteen parts by weight) are 

 combined, and sometimes even ten atoms. From 

 the extensive solvent power of water, it is scarcely 

 ever met with pure in nature. Every kind of spring 

 or river water is impregnated with saline and 

 earthy bodies of different kinds. Spring water 

 contains carbonate of lime, muriate of lime, and 

 muriate of soda, with a trace of magnesia, and often 

 a little sulphate of potash or soda. River water 

 contains carbonate of lime, muriate of soda, and 

 each of these also sometimes a little alkali. Well 

 water, besides these, contains always a portion of 

 sulphate of lime, the presence of which is the chief 

 cause of the quality termed hardness in waters. 

 Rain or snow water is freer from these foreign sub. 

 stances, but is not perfectly pure, as it affords a 

 trace of muriate of soda and muriate of lime. The 

 presence of these different sab'ne and earthy sub- 

 stances is judged of by the following tests, added 

 in the quantity of a few drops of each to an ounce 

 or two of water. A solution of nitrate of barytes 

 produces a turbid appearance from the presence of 

 any sulphate or carbonate, and the turbid appear, 

 ance of it arisinr from the latter is removed on 



