XX. On a certain excretion of carbonic acid by living plants

• Published in: Philosophical Transactions of the Royal Society of London
• Format: Article in Journal/Newspaper
• Language: English
• Published: The Royal Society 1869
• Subjects: Carbonic acid
• Online Access: http://dx.doi.org/10.1098/rstl.1869.0023; https://royalsocietypublishing.org/doi/pdf/10.1098/rstl.1869.0023

While I was engaged in some experimental determinations of the changes that take place in the composition of the Cinchona barks after being taken from the tree, a somewhat singular circumstance was noticed. Some freshly gathered barks being placed in a dish over water and covered with a bell-jar, in order to prevent loss of weight by evaporation, it was noticed that after a few hours the level of the water became depressed in the jar, and that frequent bubbles of gas escaped through the water. When it is remembered that the peculiar tannin of the cinchonæ absorbs oxygen from the air, the increase in the volume of the air appeared unaccountable. A direct experiment was therefore made, in which 5 grms. of the fresh bark of C. officinalis were placed with 11∙2 cub. centims. of oxygen over mercury and allowed to remain for twelve hours’ darkness, and seven hours’ daylight. At first a considerable absorption took place, but soon gas was given off. When the mercury stood at its original level, the gas was analyzed. It consisted of 9∙7 cub. centims. of carbonic acid, 1 cub. centim. of oxygen, and 0∙5 cub. centim. of nitrogen.