CHEMISTRY. 



11 



Klemeuu eroy, Vauquelin, and Seguin, 0.0887 ; according to 



of Davy, 0.0744. According to these various esti- 



t J7,' mates, 100 cubic inches under the mean pressure and 



""""" temperature, weigh 2.56 grains, 2.306 grains, 2.705 



grains, and 2.27 grains Troy. It is about 13 times 



lighter than common air. 



No combustible substance will burn in it ; and no 

 animal can breathe it for any length of time without 

 death. 



Formi wa- It burns when touched with a red hot iron, or 

 tcr, when brought near a flaming taper. The colour of 



the flame is yellowish, and it gives but little light. 

 If it be previously mixed with half its bulk of oxy- 

 gen gas, it burns instantaneously, and with a loud 

 explosion like the report of a pistol. If the mixture 

 be put into a strong glass cylinder, standing over 

 water, and kindled by an electric spark, the whole 

 of the two gases disappears, and the cylinder is filled 

 with the water. If the vessel be standing over mer- 

 cury, or be hermetically sealed, its inner surface be- 

 comes coated with pure water. This water was 

 found by Cavendish equal in weight to the two g.ises. 

 Hence it has been inferred, that water it a compound 

 of oxygen and hydrogen in the proportion of 7.5 by 

 weight of oxygen to 1 of hydrogen. 



and muria- When equal bulks of hydrogen and chlorine are 

 lie acid. mixed together in a glass vessel, no change takes place 

 in the dark ; but if the vessel be exposed to the sun, 

 the mixture burns with an explosion. It burns also 

 if an electric spark be pasted through it. In both 

 cases, the two gases disappear entirely ; and there is 

 found in their place a quantity of muriatic acid gas 

 almost exactly equal to them in bulk. Now, the 

 specific gravity of muriatic acid gas is almost exact- 

 ly the mean of that of hydrogen and chlorine. 

 Hence the weight does not change sensibly. From 

 this experiment it is inferred, that muriatic acid gas 

 is a compound of chlorine and hydrogen, in die pro- 

 portion of equal bulks of each in the gaseous state, 

 or by weight of 97.24 chlorine 

 2.76 hydrogen 



100.00 



Hydrogen is not sensibly altered or absorbed by 

 water. 100 cubic inches of water deprived of air 

 absorb 1.53 inches of hydrogen, according to the 

 experiments of Dr Henry. 



SECT. II. Of Carbon and Diamond. 



Carbon and ^ a P' ece ^ wo d be heated to redness in an iron 

 diamond, bottle, or a crucible filled with sand, it is converted 

 into a black brittle substance called charcoal ; the 

 propei ties of which are nearly the same from what 

 wood soever it has been obtained, provided it has 

 been exposed to a sufficiently strong heat. 

 Charcoal. Charcoal it insoluble in water, and not affected 

 (provided air be excluded) by the most violent heat 

 that can be applied. 



It conducts electricity, is not liable to putrify, 

 deprives meat of its putrid taste and smell, and is an 

 excellent tooth powder. 



It absorbs moisture with avidity, and likewise com- 

 mon air, oxypen, and hydrogen gas j but Itss of the 

 last than of the two former. 



F rms car 



When heated to 802, it takes fire ; and, if pure, Elements 

 burns all away without leaving any residuum. If the 

 experiment be made in a glass vessel filled with oxy- 

 gen gas, and the charcoal be heated by means of a 

 burning-glass, the bulk of the oxygen gas is not al- 

 tered, but a portion of it is converted into another 

 gas, possessing quite different properties. It ren- . 



ders lime-water milky, and is quite absorbed by it, 

 and cannot be breathed without occasioning instant 

 death. This gas is called carbonic acid. It very 

 nearly equals in weight the charcoal and the oxygen 

 which have disappeared. Hence it is considered as 

 a compound of them ; and, from the proportion of 

 each employed, it is considered as composed of 

 very nearly 28 parts of charcoal, and 72 of oxy- 

 gen. 



When considerable quantities of charcoal are burnt 

 in this manner, a portion of water also appears. 

 Hence it is conceived, that charcoal contains a small 

 portion of hydrogen. The constituent which con- 

 stitutes by far the greatest part of it, is called car- 

 bon. This supposition is corroborated by the late 

 experiments of Mr Davy. Carbon exists in two 

 other states, namely, the diamond and plumbago. 



2. The diamond is a precious stone, transparent, Diamond, 

 and often crystallized in a six-sided prism, terminated 



by six-sided pyramids. It is the hardest of all bo- 

 dies. Its specific gravity is about 2.3. It is a non- 

 conductor of electricity. 



When heated to the temperature of 14 of Wedge- 

 wood's pyrometer, or not so high as the melting 



?oint of silver, it gradually wastes away and burns. 

 t combines with nearly the same quantity of oxy- 

 gen, and forms the same proportion of carbonic acid 

 as charcoal. Hence it consists chiefly of carbon. 

 From the experiments of Davy, it has been infer- 

 red, that it contains a minute portion of oxygen as 

 one of its constituents. The other constituent is 

 carbon. 



3. Plumbago, called also black lead and graphite, Plumbago. 

 is well known as the substance of which pencils are 



made. It is dug out of the earth ; it is of a dark 

 blue colour, and has some metallic lustre ; it is soft, 

 brittle, and infusible. When heated to redness, it 

 gradually wastes away, and is converted into carbo- 

 nic acid, leaving a little iron behind. It seems a 

 compound of pure carbon, with about one twentieth 

 part of its weight of iron. 



Neither charcoal, diamond, nor plumbago, pro- 

 vided they be pure, are affected by chlorine. They 

 do not combine with it, and may be heated in it to 

 whiteness, without undergoing any alteration. 



Carbon combines with hydrogen, and forms a gas 

 formerly called heavy inflammable air, now carbure- 

 ted hydrogen. Various gases were formerly called 

 heavy inflammable air. The three following are the 

 chief: 



1. Carbureted hydrogen. It rises spontaneously Carburc- 

 in hot weather from stagnant water j it is evolved ted hydro- 

 during the distillation of pitcoal ; it is invisible, and S en - 

 possesses the mechanical properties of common air. 

 Its specific gravity is 0.5554. One hundred cubic 

 inches weigh 16.93 grains. For complete combus- 

 tion, it requires twice its weight of oxygen. The 

 products are its own bulk of carbonic acid and wa- 



