The Romance of Modern Chemistry

BELOW ZERO a number of hours to the temperature of liquid air, but their vitality was not destroyed by this treatment. Barley and peas have been kept for six hours in the liquid itself, and yet when they were sown subsequently in the ordinary way no falling off in the power of growth could be detected. It is possible to get a very high vacuum in a closed glass tube by simply immersing one end of it in liquid hydrogen. The boiling-point of the latter is about 100° Fahrenheit lower than the boiling-point of liquid air, and the mere contact of one end of the tube with the liquid hydrogen is sufficient to condense the air which it contains so completely that none is left in the upper part. The attainment of such low temperatures has raised the very interesting question as to what prospect there is of ever reaching the “ absolute zero.” On various grounds, chemists and physicists believe that at a certain tempera- ture, — 460° Fahrenheit, the existence of a gas as such would cease to be possible; the movements of the mole- cules, which we have learned to regard as characteristic of a gas, would be so paralysed by the intense cold as to stop altogether; the chill of death would settle on their activity. This temperature is called the “ absolute zero,11 and is in the eyes of low temperature investigators what the North Pole is to Arctic explorers. In this connection the year 1908 will be remembered as the year in which helium, the most obstinately gaseous substance known, was reduced to the liquid state. The labour expended in procuring even so little as 2 ounces of liquid helium can hardly be appreciated by the lay reader, but it may be mentioned that the preliminaries consisted in the preparation of 16 gallons of liquid air and 41 gallons of liquid hydrogen! By boiling the 191