646
THEORY AND PRACTICE OK ENGINEERING.
Book II.
Aqua regia is a mixture of nitric and muriatic acids, which has the power of dissolvinggold and platinum. Nitrogen and hydrogen combine (N + 3 II) to form ammonia; andthis gaseous compound is obtained from a mixture of quicklime and muriate of ammonia:the specific gravity of ammonia, as compared with hydrogen, is as 8*5 to 1 ; with air as•590 to 1, and 100 cubical inches weigh about 18 grains : water at a temperature of 50°will take up 670 times its volume of ammonia.
Ammonia and muriatic acid constitute the sal ammonia of commerce, or the muriate ofammonia, It is constituted of
Ammonia 1 - 17 - 31*5
Muriatic acid - 1 - 37 - 68*5
1 54 1000
Muriate of ammonia has been found serviceable in removing the incrustations formed atthe bottom of boilers, which chiefly consist of carbonate of lime. A small quantity ofsal ammoniac added to water in a boiler dissolves the carbonate formed, and converts itinto a soluble muriate, without affecting the boiler.
Sal ammoniac is made use of in tinning, to prevent the oxidation of the surface of thecopper or other metal on which it is laid.
Atmospheric air, or the atmosphere, comprising all those gaseous matters which sur-round the earth, is essentially composed of oxygen and azote, in the proportions of nearlyone of the former to four of the latter ; to which is added carbonic acid gas, and waterin the state of vapour; or the quantity of each may, under ordinary circumstances, bestated thus,
210
775
142
•8
1000*0
The pressure or weight of the atmosphere upon all parts of the surface of the earth isestimated at 15 pounds upon a square inch, which is equal to a column of mercury of the samearea, 30 inches high ; this pressure decreases as we ascend above the earth in regular geo-metrical progression ; for at three miles the density is only equal to a column of mercury,15 inches high, and at 6 only 7£ inches; at 9 miles of elevation 3^, and at 15 miles only1 inch. It has been consequently assumed that the atmosphere does not extend to a heightof more than 45 miles, and that the greatest portion of it is comprised within 15 miles.
Chlorine. , at common temperatures and pressures, is a gaseous fluid, but may be con-densed into a liquid form at a temperature of 60°, and a pressure of four atmospheres.Chlorine gas is of a greenish yellow colour; its specific gravity, as compared with air, is2*47, and 100 cubic inches at mean temperature weigh 76-59 grains. At a temperatureof 60°, water dissolves two volumes of chlorine, and the solution has a specific gravity of1*008. Chlorine has never been found pure, but in common and rock sal£ it is combinedwith sodium in the proportion of 60 per cent. ; it has a violent action on some of the metals,which, when thrown into it in a state of powder, are burnt, and enter into combinationwith it.
Chlorine destroys most animal and vegetable colouring matters, as well as odorouseffluvia, by decomposing them, removing the hydrogen present, or by combining with theoxygen. Water absorbs about l£ times its volume of chlorine.
Protoxide of Chlorine ( hypochhrov.s acid) is pernicious to respiration ; water dissolves tenvolumes of this gas, which is of deep yellow colour ; it destroys most vegetable colours, pre-viously reddening the blues. The aqueous solution is rapidly decomposed by iron filings,but the other metals have little or no action upon it. Silver , however, combines with thechlorine, evolving at the same time a portion of its oxygen. Bromine, iodine, sulphur,phosphorus, selenium, and arsenic, are converted by it into their respective acids, chlorinebeing evolved.
Chlorine - 1
36
81*75
Oxygen - 1
8
18*25
1
44
100-00
Peroxide of Chlorine is gaseous, transparent, and of a
very deep greenish yellow colour.
Its specific gravity, as compared with air,
is 2*360; as
compared
with hydrogen it is 34
to 1.
Chlorine - 1
36
52*9
1
Oxygen 1
32
47-1
2
1
68
100*0
2