|LIQUEFACTION OF GASES - CAILLETETS EXPERIMENTS.
We recently laid before our readers full details of the very important experiments made by M. Raoul Pictet,
which resulted in the liquefaction of oxygen, air, and other gases hitherto supposed to be permanent. We also noted that simultaneously with M. Pictet, who carried on his investigations in Geneva, M. Cailletet, of Paris, had experimented in the same direction, though by different means, and had obtained similarly successful results.
M. Cailletet is engaged in iron manufacturing, and his researches were conducted at his foundery at Chatillon-sur-Seine. The apparatus used by him is represented in the annexed engravings, for which we are indebted to La Nature. A hollow steel cylinder, A, Fig. 1, is solidly fixed on a cast iron frame by the straps, B. This is filled with water, and entering it is a soft steel plunger, to the extremity of which is attached a heavily-threaded screw, which enters the bronze nut, F, of the large hand wheel, NI. The nut is prevented from horizontal motion and is held in a heavy strap, as shown, so that when it is rotated by turning the hand wheel it causes the screw to move forward or back, and so moves the plunger into or out of the cylinder. A leather washer inside the latter prevents any escape of the liquid within. In order to introduce the water or other fluid to be compressed into the cylinder, it is poured into the receiver, G, which communicates with the interior, the passage being closed at will by a conical steel screw operated by the hand wheel, 0. By this means compressed gases may be suddenly allowed to expand and to produce an intense fog in the capillary tube inclosed in the glass cylinder, rn. This fog is formed under the influence of the exterior cold produced by the sudden expansion, and is a sure sign of the liquefaction or even congelation of the gases hitherto regarded as permanent. The other portions of the apparatus may briefly be described as follows:
a is a hollow steel reservoir capable of supporting a pressure of 900 or even 1,000 atmospheres. It is connected to the compression apparatus by a metallic capillary tube. Water, under the action of the plunger, enters this reservoir and acts on mercury, which compresses the gas. b is the adjutage which receives the glass vessel which contains the gas experimented upon. A screw serves to fix this piece to the upper part of the reservoir. Fig. 2 shows this arrangement half its natural size. rn is a glass cylinder containing another cylinder in which is the fine tube in which the gas is liquefied. This capillary tube may thus be surrounded by liquid protoxide of nitrogen and other refrigerating liquids. The exterior cylinder contains moisture-absorbing material so as to prevent a deposit of ice or vapor on the cooled tube, which would hinder observation. p is a cast iron tablet which supports the reservoir, a. Screws, d d, allow of lifting or lowering the reservoir for spectroscopic examination. An adjutage, 5, unites the metallic capillary tubes and transmits the pressure to the different parts of the apparatus. N is a Thomasset manometer modified and verified by means of a free air manometer established on a hillside near the laboratory. N represents a glass manometer which serves to control the indications of the first mercury apparatus.
No danger attends the use of this machine, as the glass tube in which the gas is compressed presents but a very small surface and would do no harm if it broke.
In discussing these experiments in our former issue we referred to Dr. Andrews experiments. One of the chief deductions made by him was that there existed for permanent gases a critical point of pressure and temperature above which they could not be brought to a liquid state. N. Cailletets experiments have confirmed this, and proved that for every gas a certain pressure must be combined with a certain lowering of temperature. Neither influence alone is sufficient to produce the desired result, no matter what the intensity may be. M. Cailletet first liquefied nitric oxide. This gas remained gaseous at the pressure of 270 atmospheres and at a temperature of 46.4° Fah. Marsh gas, on the other hand, liquefied at 180 atmospheres and 44.6° Fah.
If oxygen or pure carbonic oxide be inclosed in the compression apparatus, says M. Cailletet, if these gases be brought to the temperature of -20,2° Fah. by means of sulphurous acid and under a pressure of about 300 atmospheres, both will retain their gaseous state. But if they be subjected to sudden expansion, which according to Poissons formula should produce a temperature of at least 392° Fah. below that existing, an intense fog is at once seen, due to their liquefaction and possibly to their solidification. The same phenomenon is observed on the expansion of carbonic acid, and nitrous and nitric oxides when strongly compressed. Shortly after having obtained this result, M. Cailletet announced to the French Academy of Sciences his success in liquefying nitrogen, atmospheric air, and even hydrogen itself, hitherto found the most refractory of all gases. M. Cailletet furnishes the following details to the Comptes Rendus of the French Academy:
Nitrogen.-Pure or dry nitrogen compressed to about 200 atmospheres at a temperature of 55.4° Fah., then expanded suddenly, condenses and appears first in the form of spray, in drops of appreciable volume. This liquid disappears gradually, its vanishing beginning at the exterior and extending toward the center, until finally a single vertical column remains in the axis of the tube for a few seconds.
Hydrogen.-This gas compressed to 280 atmospheres and expanded gives a thick fog throughout the entire tube, which however suddenly disappears.
Air.-Atmospheric air was first dried and deprived of all traces of carbonic acid, and then treated as above described. The data of temperature, etc., we have already given in our previous article.
In Fig. 3 is illustrated a small and simple apparatus designed by M. Cailletet, which may be used for exhibiting the liquefaction of gases before a class. It is an exact copy of the parts, a and ~n, of the large apparatus shown in Fig.
1. The glass cover is modified and the screw press is replaced by a pump. T T is a glass tube filled with the gas to be compressed, it being previously traversed by a gaseous current until all air is expelled. To this end it is first placed in a horizontal position; when it is full of gas, the end, P. is sealed up hermetically by heat, and the other end is held closed by the finger until it is introduced in the wrought iron device below and enters a cylindrical hollow containing mercury. The upper part of the tube is enveloped in a glass cylinder, M, which is filled with a refrigerating mixture, and over all is placed the bell glass, G. The tube, T U, is connected with the hand compressing pump, which is provided with a suitable manometer. The water compressed by the pump acts on the upper part of the mercury, as shown by the horizontal lines in our figure. The mercury is thus driven into the tube, T T, and reduces the space occupied by the gas. It soons becomes covered with little drops of the compressed vapor, which unite in a liquid mass, b.
B is a block of very resistant forged iron; E and E are screws which allow of the apparatus being taken apart; A is an adjutage; P P, three legged strong support for the apparatus; 5, support for the bell, G, and cylinder, M; N, supplementary screw designed to close the aperture, R, when mercury is placed in the apparatus. The large lower portion of the tube, T, being subjected to equal pressure within and without, cannot break, and the only portion open to rupture is the small upper part of the tube, which may be made exceedingly strong. The experiment may, by the electric or oxyhydrogen light, be projected on a screen, when all the phenomena may be followed by the eye without incurring any danger through breakage.
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