Service chemistry : being a short manual of chemistry and metallurgy and their application in the naval and military services / by Vivian Byam Lewes and J.S.S. Brame.

Vivian Byam Lewes

Date:: 1913

Credit: Service chemistry : being a short manual of chemistry and metallurgy and their application in the naval and military services / by Vivian Byam Lewes and J.S.S. Brame. Source: Wellcome Collection.

102/622 page 80

$and the moist metal oxidised so rapidly that snfdcienli heat was j>;enerated l-o form considei'able quantities of vapour, and to give rise to serious hairs as to the softeiiing of the insulating material of the coi’e. Slow Combustion.—Many cases of chemical combination with the oxygen of the air take place in Natui’e, wliich are so slow that the heat evolved during the action escapes our senses, and indeed all cases of decay are processes of this kind, and the action is termed sloio combustio7i. A tree left to rot upon the ground gradually disappears in the course of years, being mainly oxidised into gaseous products such as carbon dioxide and water vapour, and }^et scarcely any evolution of heat is observed, although the same amomit of heat is generated as if the tree had been cut into logs and burnt. Respiration, and the Circulation of the Blood.—Ajiother example of slow combustion is found in the canying on of life by respiration, and the circulation of the blood. The blood is distributed by the arteries, which carry blood from the heart to the body, while the veins bring the blood back to the heart ; between the extremities of the arteries and the commencement of the veins we find a minute system of vessels, called the “ capil- laries,” which connect the arteries and the veins. The heart is divided into four chambers, and the blood is brought to the heart by two great veins, one from the lower and the other from the upper extremities ; these empty themselves into the right- hand upper chamber ; from this it passes into the right-hand lower chamber, whence it passes through a vessel which terminates in the capillaries of the lungs. These capillaries communicate with four large veins which bring the blood back to the left-hand upper chamber of the heart, whence it passes into the left-hand lower chamber, and is forced out into the great arteiy, which distributes it to the different organs and tissues of the body. In the lungs the blood comes in contact with the inhaled aii\ admitted to the air-ceUs of the lungs by tlu' windpi])e, and here a great change takes place in the character of the blood : the blood as it comes into the lungs is purjde, and is charged with carbon dioxide, but in the air-cells of the lungs this gas passes out from the blood and oxygen passes in b_y dilfusion, and takes its place, whilst the colour of the blood turns from purple to red, and passes back through the heart to the arteries and the system ;$