Why is the sea salt? / by William Mackie.

  • Mackie, William.
Date:
1902
Catalogue details

Licence: In copyright

Credit: Why is the sea salt? / by William Mackie. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

    8/31 (page 4)
    Again, as regards phosphates and chlorides, the mineral apatite, which is a double phosphate and chloride (or fluoride) of lime, imder atmospheric agencies breaks up into carbonate c£ lime, phosphoric acid, and chloride of lime. The phosphoric acid so Hberaited meeting with alkaline carbonates will give rise to the coiTesponding alkaline phosphates. Sodalite is also another cldorine-containing mineral which is found in some recent volcanic rocks. Another source of chlorine is from the liquid present in the pores of the quartz of such rocks as granite. In such quartz grains countless numbers of minute cavities are seen filled, or partially filled, with fluid. Tliis fluid is known to contain chlorides—in fact, it is often saturated with sodium and potassium chlorides, and in some cases we even find small cubes of these salts lying loosely in these httle interspaces. Where that occiu's we know the fluid has once been supersaturated with chlorides, and the excess has ciystallized out on cooling. Then, again, in the case of volcanoes, we have hydrochloric acid vapours given off at certain stages of their action. These are no doubt derived from the decomposition of chlorides, but as to whether these are of cosmic origin or derived from the decomposi- tion of inflowing sea water, which, according to one theory, is an element in the cause of a particular phase of volcanic action, must needs remain an open question. Of nitrates, more than one source may be found. By actual experiment in the chemical laborator}^, we find if we pass an electric spark through air that the oxygen and nitrogen imite to form nitrogen pentoxide, and this in the presence of water be- comes nitric acid. The acid so formed, acting upon alkaHne car- bonates, gives rise to the corresponding nitrates. Of course it will be easily seen that all the conditions exist in Nature for the formation of nitrates in this way, and insignificant possibly though the amount be that is so produced, one has always greater faith in what can be actually demonstrated in the chemical laboratory. It is, nevertheless, certain that nitrates are also formed by the oxida- tion of nitrogenous organic matter. In proof of this we have only to cite the methods ad(^ted by the French chemists for the preparation of nitre for making gunpowder at a time when, being at war with this country, the French nation was cut off from the natural supplies. In much the same way probably most of the nitrates existing in Nature have been produced, as, foi example, in the nitre beds of India and Chili. Analyses of surface waters always show more or less organic matter, which, tliough variable both in kind and quantity, is almost always less in amount tlian the inorganic salts present.