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Updated: May 5, 2025
We notice now three of the chief chemical processes concerned in weathering, solution, the formation of carbonates, and oxidation. SOLUTION. Limestone, although so little affected by pure water that five thousand gallons would be needed to dissolve a single pound, is easily dissolved in water charged with carbon dioxide. In limestone regions well water is therefore "hard."
In slightly acid, neutral, or alkaline solutions on the other hand, protoxide of manganese absorbs oxygen with great avidity and forms with it different compounds, according to the means of oxidation employed.
In places, however, it is warm, for when the oxygen of the air reaches the fresh sulphide it begins to oxidize the ore; that is, it begins to burn it, and change it into a different compound, just as fire changes wood or coal. Wherever oxidation is going on, heat is produced. Fresh air is constantly needed in these workings far underground.
Why is it that the oxidation of starch in the living machine gives rise to motion, growth, and reproduction, while if the oxidation occurs in the chemist's laboratory, or even in a bit of dead protoplasm, it simply gives rise to heat? One of the primary questions to demand attention in this search is whether we are to find the explanation, at the bottom, a chemical or a mechanical one.
Light a splinter and, slipping the cover to one side, thrust the flame into the jar of nitrogen, noting the effect. What purpose is served by each in the atmosphere? Phosphorus.—Examine a small piece of phosphorus, noting that it has to be kept under water. Lay a small piece on the table and observe the tiny stream of white smoke rising from it, formed by slow oxidation.
And in proportion as the thermal loss is great, must the quantity of these matters required for oxidation be great. But the power of the digestive organs is limited. Consequently, when they have to prepare a large quantity of this material needful for maintaining the temperature, they can prepare but a small quantity of the material which goes to build up the frame.
Fat and starch may be oxidized in a chemist's test tubes, and will there liberate energy; but they do not, under these conditions, manifest vital phenomena. Proteid may be brought in contact with oxygen without any oxidation occurring, and even if it is oxidized no motion or assimilation or reproduction occurs under ordinary conditions.
It was therefore only necessary for our biological chemists to suppose that their chemical compound protoplasm possessed the power of causing certain kinds of oxidation to take place, just as water itself induces a simpler kind of oxidation, and they would have a mechanical explanation of the life activities.
The comparison of the acid and alkali solutions was made, using methyl orange as an indicator, while the titration of the oxalic acid is made with the use of phenolphthalein. In the oxidation processes of volumetric analysis standard solutions of oxidizing agents and of reducing agents take the place of the acid and alkali solutions of the neutralization processes already studied.
Chemical changes in the blood and tissues are constant vital phenomena; increased oxidation causes increased activity of the circulation, increase of temperature, increase of urea and carbonic acid in the economy from retrograde changes, and, finally, during menstrual life the flow of blood from the uterus carried off the effete materials from the highly charged system.
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