Lectures on the influence of researches in organic chemistry on therapeutics : especially in relation to the depuration of the blood / delivered at the Royal College of Physicians, by Golding Bird.

Bird, Golding, 1815-1854.

Date:: 1848

Credit: Lectures on the influence of researches in organic chemistry on therapeutics : especially in relation to the depuration of the blood / delivered at the Royal College of Physicians, by Golding Bird. 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.

15/44 (page 15)

$B are capable of uniting and forming a new and stable compound, yet it may happen that their chemical tendency is so slight that we may actually place them in contact without their combining, or presenting the slightest attractive force for each other. But if we take a compound of A with C, and place B in contact at the instant C is by some force separated from A, they will at once unite and form the new combination. Thus it is assumed that the chemical tendency or polarity of bodies is most active and intense at the moment of their separation. And we must not lose sight of the fact, that at the moment of this separation being effected, electricity is always evolved,—a circumstance to which I had frequent occasion to draw attention in the last course of lectures I had the honour to deliver in this College. Now, the view I have thus announced involves no wild hypothesis, nor requires any demand on your credulity for its admission. It is not only a well-recognised law, but one which presides over a vast number of pheno- mena. Its importance is so great that I hope an illustration or two may not be deemed out of place. In the vessel before me is a solution of arsenious acid; through this a current of hydrogen gas is now passing, and the gas as it escapes readily inflames on holding a lighted taper near it. It burns with the well-known flame of burning hydrogen, and on holding a plate of glass over it steam is condensed upon it, shewing that water is formed by the union of the hydrogen with the oxygen of the acid. Not a particle of arsenic is removed from the solution by the gas, shewing that the chemical tendency of the hydrogen for the metal is at a mini- mum. I will now pour a few drops of the arsenical solution into the flask containing the ingredients from which the hydrogen gas is evolved; re-adjusting the apparatus, I again inflame the gas. You see the colour of the flame has changed into a lurid blue, as if expressive of the deadly character of the agent it is liberating ; and on holding a plate of glass over it, a steel-coloured ring of metallic arsenic is depositedupon it. Now, in what did the conditions from these two variations of the experiment differ ? In the first, the hydrogen, within the fraction of a second of time from its evolution, traversed the arsenious fluid without taking up a por- tion of the metal. In the second, the hydro- gen, at the very instant of its separation from the oxygen of the water,—at the moment of time when its chemical polarity was at its extreme intensity,—came in contact with the arsenious acid, and seizing the metal with avidity, carried it off as gas. This condition has been long known to chemists as the nascent slate of matter, but it has hardly been invested with its due importance; aided by it we are enabled to recognise in dead matter something generally regarded as the attribute alone of vitality. Many more instances of its sway will atonce rush to your minds. Thus, I have here some pure ether, or oxyde of ethyle (AeO) ; in the bottle by its side is a very fluid fragrant acetic ether, or acetate of oxyde of ethyle (AeO, A), consisting of an equivalent of ether com- bined with an equivalent of acetic acid. If I now pour some acetic acid upon the ether in the glass before me, they do not combine, and you can readily observe the oxyde of ethyle floating on the acid, as if they had no affinity for each other. Yet their mutual affinity is really very great when we exalt their chemical tendency to the utmost, by presenting the oxyde of ethyle to the acid in a nascent state. Thus, if I place in another vessel some crystallizable acetic acid and alcohol—which is a hydrate of oxyde of ethyle (iEeO, HO)—then add some sul- phuric acid, the latter will separate the water, and the oxyde of ethyle thus set free will at the instant of its separation—when its chemical tendency is exalted to the highest degree—enter with the acetic acid, and the fragrant odour of the acetate of oxyde of ethyle will at once shew that the combination has been effected. Again, alcohol is a true combination of ether and water — a hydrate of oxide of ethyle; yet if I mix ether and water, not only is alcohol not formed, but they do not even mix mechanically. To ensure this combination, the oxide of ethyle must meet the water in the condition to which I have alluded. Thus, if I add some hydrate of potass to acetic ether (AeO, A), the potass seizes the acetic acid to form acetate of potass (KO, A) ; and the oxide of ethyle, at the moment of its evolution, seizes the water with intense force, and reconstitutes alcohol. Another familiar but remarkable illustration of the important results of this state of chemical elements in the nascent state, is shewn in the well-known process for the manufacture of sulphuric acid. Sulphur burned in the air will always evolve fumes of sulphurous acid (S02), and by no varia- tion of the experiment can we succeed in combining it with another atom of oxygen. But if we bring in contact with it hypo- nitrous acid (N03), the third atom of oxygen always held loosely combined, is given up, and in its nascent state unites with the sulphurous acid to form sulphuric acid (SO.). Most of the animal fats are composed of a base called the oxide of lipyle, and some peculiar fatty acid. Thus, mutton fat is a stearate of oxide of lipyle, and nothing is easier than to separate these bodies; the stearic acid forming the mass of crystalline$