powdered in a mortar. By its aid a complete trituration of the typhoid bacilli has been accomplished at the Jenner Institute, and the same process, already applied with success also to yeast cells and animal cells, is being extended in other directions.
Industrial Applications.—While liquid air and liquid hydrogen are being used in scientific research to an extent which increases every day, their applications to industrial purposes are not so numerous. The temperatures they give used as simple refrigerants are much lower than are generally required industrially, and such cooling as is needed can be obtained quite satisfactorily, and far more cheaply, by refrigerating machinery employing more easily condensable gases. Their use as a source of motive power, again, is impracticable for any ordinary purposes, on the score of inconvenience and expense. Cases may be conceived of in which for special reasons it might prove advantageous to use liquid air, vaporized by heat derived from the surrounding atmosphere, to drive compressed-air engines, but any advantage so gained would certainly not be one of cheapness. No doubt the power of a waterfall running to waste might be temporarily conserved in the shape of liquid air, and thereby turned to useful effect. But the reduction of air to the liquid state is a process which involves the expenditure of a very large amount of energy, and it is not possible even to recover all that expended energy during the transition of the material back to the gaseous state. Hence to suggest that by using liquid air in a motor more power can be developed than was expended in producing the liquid air by which the motor is worked, is to propound a fallacy worse than perpetual motion, since such a process would have an efficiency of more than 100%. Still, in conditions where economy is of no account, liquid air might perhaps, with effectively isolated storage, be utilized as a motive power, e.g. to drive the engines of submarine boats and at the same time provide a supply of oxygen for the crew; even without being used in the engines, liquid air or oxygen might be found a convenient form in which to store the air necessary for respiration in such vessels. But a use to which liquid air machines have already been put to a large extent is for obtaining oxygen from the atmosphere. Although when air is liquefied the oxygen and nitrogen are condensed simultaneously, yet owing to its greater volatility the latter boils off the more quickly of the two, so that the remaining liquid becomes gradually richer and richer in oxygen. The fractional distillation of liquid air is the method now universally adopted for the preparation of oxygen on a commercial scale, while the nitrogen simultaneously obtained is used for the production of cyanamide, by its action on carbide of calcium. An interesting though minor application of liquid oxygen, or liquid air from which most of the nitrogen has evaporated, depends on the fact that if it be mixed with powdered charcoal, or finely divided organic bodies, it can be made by the aid of a detonator to explode with a violence comparable to that of dynamite. This explosive, which might properly be called an emergency one, has the disadvantage that it must be prepared on the spot where it is to be used and must be fired without delay, since the liquid evaporates in a short time and the explosive power is lost; but, on the other hand, if a charge fails to go off it has only to be left a few minutes, when it can be withdrawn without any danger of accidental explosion.
For further information the reader may consult W. L. Hardin, Rise and Development of the Liquefaction of Gases (New York, 1899), and Lefèvre, La Liquéfaction des gaz et ses applications; also the article Condensation of Gases. But the literature of liquid gases is mostly contained in scientific periodicals and the proceedings of learned societies. Papers by Wroblewski and Olszewski on the liquefaction of oxygen and nitrogen may be found in the Comptes rendus, vols, xcvi.-cii., and there are important memoirs by the former on the relations between the gaseous and liquid states and on the compressibility of hydrogen in Wien. Akad. Sitzber. vols. xciv. and xcvii.; his pamphlet Comme l’air a été liquéfié (Paris, 1885) should also be referred to. For Dewar’s work, see Proc. Roy. Inst. from 1878 onwards, including “Solid Hydrogen” (1900); “Liquid Hydrogen Calorimetry” (1904); “New Low Temperature Phenomena” (1905); “Liquid Air and Charcoal at Low Temperatures” (1906); “Studies in High Vacua and Helium at Low Temperatures” (1907); also “The Nadir of Temperature and Allied Problems” (Bakerian Lecture), Proc. Roy. Soc. (1901), and the Presidential Address to the British Association (1902). The researches of Fleming and Dewar on the electrical and magnetic properties of substances at low temperatures are described in Proc. Roy. Soc. vol. lx., and Proc. Roy. Inst. (1896); see also “Electrical Resistance of Pure Metals, Alloys and Non-Metals at the Boiling-point of Oxygen,” Phil. Mag. vol. xxxiv. (1892); “Electrical Resistance of Metals and Alloys at Temperatures approaching the Absolute Zero,” ibid. vol. xxxvi. (1893); “Thermoelectric Powers of Metals and Alloys between the Temperatures of the Boiling-point of Water and the Boiling-point of Liquid Air,” ibid. vol. xl. (1895); and papers on the dielectric constants of various substances at low temperatures in Proc. Roy. Soc. vols. lxi. and lxii. Optical and spectroscopic work by Liveing and Dewar on liquid gases is described in Phil. Mag. vols. xxxiv. (1892), xxxvi. (1893), xxxviii. (1894) and xl. (1895); for papers by the same authors on the separation and spectroscopic examination of the most volatile and least volatile constituents of atmospheric air, see Proc. Roy. Soc. vols. lxiv., lxvii. and lxviii. An account of the influence of very low temperatures on the germinative power of seeds is given by H. T. Brown and F. Escombe in Proc. Roy. Soc. vol. lxii., and by Sir W. Thiselton Dyer, ibid. vol. lxv., and their effect on bacteria is discussed by A. Macfadyen, ibid. vols. lxvi. and lxxi. (J. Dr.)
LIQUORICE. The hard and semi-vitreous sticks of paste,
black in colour and possessed of a sweet somewhat astringent
taste, known as liquorice paste or black sugar, are the inspissated
juice of the roots of a leguminous plant, Glycyrrhiza glabra, the
radix glycyrrhizae of the pharmacopoeia. The plant is cultivated
throughout the warmer parts of Europe, especially on the
Mediterranean shores, and to some extent in Louisiana and
California. The roots for use are obtained in lengths of 3 or 4 ft.,
varying in diameter from 14 to 1 in.; they are soft, flexible and
fibrous, and internally of a bright yellow colour, with a characteristic,
sweet pleasant taste. To this sweet taste of its root the plant
owes its generic name Glycyrrhiza (γλυκύῤῥιζα, the sweet-root),
of which the word liquorice is a corruption. The roots contain
grape-sugar, starch, resin, asparagine, malic acid and the
glucoside glycyrrhizin, C24 H36 O9, a yellow amorphous powder
with an acid reaction and a distinctive bitter-sweet taste. On
hydrolysis, glycyrrhizin yields glucose and glycyrrhetin.
Stick liquorice is made by crushing and grinding the roots to a pulp, which is boiled in water over an open fire, and the decoction separated from the solid residue of the root is evaporated till a sufficient degree of concentration is attained, after which, on cooling, it is rolled into the form of sticks or other shapes for the market. The preparation of the juice is a widely extended industry along the Mediterranean coasts; but the quality best appreciated in the United Kingdom is made in Calabria, and sold under the names of Solazzi and Corigliano juice. Liquorice enters into the composition of many cough lozenges and other demulcent preparations; and in the form of aromatic syrups and elixirs it has a remarkable effect in masking the taste of nauseous medicines.
LIQUOR LAWS. In most Western countries the sale of
alcoholic liquor is regulated by law. The original and principal
object is to check the evils arising from the immoderate use of
such liquor, in the interest of public order, morality and health;
a secondary object is to raise revenue from the traffic. The
form and the stringency of the laws passed for these purposes
vary very widely in different countries according to the habits
of the people and the state of public opinion. The evils which
it is desired to check are much greater in some countries than
in others. Generally speaking they are greater in northern
countries and cold and damp climates than in southern and
more sunny ones. Climate has a marked influence on diet for
physiological reasons over which we have no control. The fact
is attested by universal experience and is perfectly natural and
inevitable, though usually ignored in those international comparisons
of economic conditions and popular customs which have
become so common. It holds good both of food and drink. The
inhabitants of south Europe are much less given to alcoholic
excess than those of central Europe, who again are more
temperate than those of the north. There is even a difference
between localities so near together as the east and west of
Scotland. The chairman of the Prison Commissioners pointed
out before a British royal commission in the year 1897 the
greater prevalence of drunkenness in the western half, and
attributed it in part to the dampness of the climate on the
western coast. But race also has an influence. The British
carry the habit of drinking wherever they go, and their colonial
