in the pot is used as pitch. The light oil, called ‘pinoline,’ is rectified, and the acetic acid water passing over with it is saturated with calcium hydrate, filtered and evaporated to dryness; and the calcium acetate obtained is employed in the manufacture of acetic acid. The rosin oil, obtained after the light oil has passed over, has a dark violet-blue colour, and is called ‘blue rosin oil.’ The red oil is boiled for a day with water, the evaporated water being returned to the vessel; next day the water is drawn off, and the remaining rosin oil is saponified with caustic soda lye of 36° Baumé, and the resulting solid mass is distilled so long as oil passes over.
The product obtained is ‘rectified rosin oil,’ which is allowed to stand in iron vessels, protected by a thin layer of gypsum, whereby after a few weeks a perfectly clear oil is obtained free from water. The oil of first quality is obtained by a repetition of the foregoing operation upon the once rectified oil. The residues of both operations are melted up with the pitch.[137]
[137] Dingler’s ‘Polytech. Journ.,’ ccvi, 246 (‘Journ. Chem. Soc.,’ new series, vol. xi, 304).
Rosin oil is employed in the manufacture of axle grease, the oil being previously converted into a soap by heating with slaked lime.
RESOLV′ENTS. Syn. Discutients; Resolventia, L. Substances or agents which discuss or resolve inflammatory and other tumours. See Digestives.
RESPIRA′TION. The peculiar function by which the blood is submitted to the action of the air, for the purpose of removing carbonic acid, and restoring its vitality by the absorption of atmospheric oxygen.
The air expired from the lungs is found to have undergone a most remarkable change. It is now loaded with aqueous vapour, whilst a considerable portion of its oxygen has disappeared, and its place is supplied by about a like volume of carbonic acid. It is no longer capable of supporting animal life, and even a lighted taper plunged into it is immediately extinguished. In the mean time the ‘venous blood’ which entered the lungs from the right chambers of the heart has lost its dingy hue, and has acquired the rich florid colour which is characteristic of ‘arterial blood.’ In this state it is returned to the left chambers of the heart, and is propelled by that organ to every part of the body, from which it passes by the capillaries to the veins, and by these again to the heart and lungs, to undergo the same changes and circulation as before. The carbon and hydrogen of the blood, ultimately derived from the food, are, in this course, gradually converted into carbonic acid and water by a species of slow combustion; but how these changes are effected is not definitely ascertained.
The lungs, as is well known, receive the atmospheric air through the trachea or windpipe. At the root of the neck this divides
into two branches, called bronchi, and each bronchus, upon entering its respective lung, divides into an infinity of small tubes. The latter terminate in small pouches, called the air-cells, and a number of these little air-cells communicate together at the extremity of each small tube. The number of air-cells in the two lungs has been estimated at 1,744,000,000, and the extent of the membrane which lines the cells and tubes together at 1500 square feet. (Dr Addison.) Under ordinary circumstances, from 22 to 43 cubic inches of air are thrown out at each expiration; but, by a forced effort, 50 or 60 inches are ordinarily expelled. The number of respirations per minute in health, when the individual is tranquil and undisturbed, is about 15. Exercise increases this number. See Food, Nutrition, &c.
Respiration, Artificial. Various means have been adopted for this purpose, among which blowing air into the lungs is, perhaps, that generally adopted. A better, and, in general, a much more efficient method, is as follows:—Powerful but not violent pressure is made upon the sides of the chest and upon the abdomen at the same time, by which the cavity of the thorax is diminished, and the air contained in the lungs is expelled; the compression is then suddenly withdrawn, when the elasticity of the ribs causes them to resume their old expanded positions; the chest is again enlarged, a partial vacuum is formed, and air rushes into the lungs, to be again expelled by pressure upon the ribs and abdomen as before. By this means artificial respiration may be kept up for a great length of time, without the use of bellows, or any other apparatus. The chief principle of Dr Marshall Hall’s so-called ‘ready method’ is the postural performance of artificial respiration. The patient is first placed gently on the face, and then turned on the side; then on the face again, alternately; these measures being repeated deliberately, efficiently, and perseveringly, fifteen times in the minute. When the prone position is resumed, equable, but efficient, pressure is applied along the spine; this pressure is removed immediately before rotation on the side.