SCIENCE FOR THE PEOPLE.

Otago Witness, Issue 1242, 18 September 1875, Page 3

SCIENCE FOR THE PEOPLE.

Carbon and Carbonic Acid.

Carbon is found4n nature in three distinct forms, so different one from the other, that we are not able to tell by the mere appearance that they are the same substance. What do you think when I tell you that the beautiful bright sparkling gem which we call the diamond is nothing more than this piece of coal, that is, chemically it is the same in substance, namely, carbon in its purest form. Coal or charcoal is another form of carbon, and then we have that substance which we use to make black lead pencils, and for blacking grates, commonly and improperly called " black-lead," for their is no lead in it, or otherwise plumbago or graphite. These things are nothing more than carbon, or diamond in another form, a. form not so valuable, because it occurs in larger quantities, but perhaps even more useful than the diamond, though the diamond is a useful substance, because it is the hardest body we know of in the world : it is so hard that it will cut glass, and without it the glaziers would be in a difficulty. We cannot imagine things more different in appearance than blacklead, charcoal, and diamond, and yet these substances are actually one and the same carbon.

Those who have attended these lectures and attended to them— which is another thing— will know what happens when the carbon or charcoal burns ; they will know that the beautiful bright sparkling is the result of the combination of carbon with the oxygen, in the air, and that a substance is formed, the name of which I have written on the board — carbonic acid; and this carbonic acid is produced whenever substances containing carbon burn in the air or in oxygen ; and it does uot matter whether we burn diamond in oxygen or, charcoal, or graphite in oxygen the same thing takes place — namely, carbonic acid is formed And what is more important, the same weight of carbonic acid is formed when we burn a certain weight of either diamond, charcoal, or graphite. If we were rich enough to burn 12lbs of diamond — it would be a costly experiment, but the experiment has been performed with a smaller quantity, — how much carbonic acid should we get? Why, we should get exactly 441b. I have put this down on the syllabus, because it is so important—" 121b 6f diamond, charcoal, or graphite, would yield 441bs of carbonic acid." This is one of the reasons why chemists have come to the conclusion that these substances are one and the same, because they yield the same quantity of the like produot ; hence they must be the same substance. — Prof. Roscoe's Lectures to Working Men.