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
Catalogue details

Licence: Public Domain Mark

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.

    8/44 (page 8)
    Still this does not tell us any of the proper- ties of the compound, nor inform us of the molecular arrangement of its elements. But all this is at once afforded us by its rational formula N H4 0 + C4 H„ 03, which tells us at a glance, that the body is a compound of oxyde of ammonium and acetic acid, and without any further trouble, gives us every possible information of the nature and properties of the volatile body. Such investigations into the constitution of matter bring us in contact with a most difficult question, and one which can only be deter- mined by long and laborious research. I refer to the grouping of the constituent atoms. We are acquainted with bodies hav- ing the same chemical composition, and yet possessing properties so distinct, that it is at once evident that however identical may be their chemical composition, their chemical constitution must be totally different,—a difference to be explained alone by the different grouping of their atoms. Such in- stances of isomerism and polymerism are familiar to us ; as one example, I might men- tion urea and cyanate of ammonia, both consisting of the same number of elements, but so differently grouped, as to produce in the one a weak saline base, and in the other a neutral salt. Again, hydrated glycocoll, or sugar of gelatine, a body which in all pro- bability plays very important part in the series of metamorphic changes occurring in the body, has the same composition as the hyponitrite of ethyle, or C.H.N, 04, and yet how utterly different in chemi- cal and physiological properties, is the diuretic and diffusible fluid existing in the common sweet spirits of nitre, from the white crystalline powder of glycocoll I now shew you ; they have but one sensible attri- bute in common, that of sweetness. 1 feel that I owe an apology for trespassing upon your time by this digression, but the only one I can offer is founded on the fact, that chemistry has of late years made such rapid strides, as almost to require a new language for expressing its facts : and hence the distinctions between formulae upon which I am anxious to insist much in the course of these lectures, would scarcely be intelligible to those whose other engagements have prevented their keeping up in this rapid race. There is, however, one other curious and remarkable fact connected with the effects of grouping of atoms, and the important re- sults flowing from this apparently very in- significant influence, that I cannot avoid alluding to it, especially as it renders, by an example of contrast, less startling the fact that properties so very different are exerted by bodies nearly alike in chemical composi- tion, of which we see so many examples in the products of animal life. It would ac- tually appear, if a group of atoms are built up in a certain manner, that if we can withdraw one and replace it by an atom of a totally different substance, but so as not to disturb the arrangement of the whole, we obtain a new body, but one which would appear to possess analogous physiological effects, if taken into the system of an animal. A sort of substitution, like that which might be effected by replacing a brick from a house, by a mass of granite of equal size, without disturbing the structure of the edifice. Thus in a series of experiments lately performed by a very laborious and ingenious observer, Mr. Blake, it appears probable that isomorphous bodies, or in other words, bodies whose atoms are similarly grouped, exert nearly analogous actions on the animal economy. He thus made the start- ling discovery that bodies, even if poisonous, might be injected into the veins of an animal, without producing any very serious effects, providing they were isomorphous with some of the normal blood constituents : the reverse being also true. Thus even arsenic acid may be injected without pro- ducing any important results, in consequence of its isomorphism with the phosphoric acid of the blood ; while, on the other hand, a few grains of a salt of baryta (a much less poisonous body), would, from its hetero- morphism, almost instantly arrest the action of the heart. We are acquainted with a most remark- able illustration of the influence of the grouping of atoms in developing or masking the effects of a poisonous body in the case of the compounds of kakodyl. When equal parts of arsenious acid and acetate of potass are distilled, a most remarkable body is obtained. This consists chiefly of an oil- like fluid, evolving most offensive fumes, and so inflammable as to burst into flame on exposure to the air. This body consists of C4 H6 As2 0„ and is regarded as a compound of a peculiar body termed kakodyl (C„ H0 As2) with oxygen, or Kd + O. This body possesses in perfection all the poisonous properties of the arsenic it contains ; and great caution is required on the part of the chemist to avoid being poisoned by its fumes whilst preparing it. But if this body be kept for some time under water, it absorbs two atoms of oxygen and one of water, and deposits crvstals of kakodylic acid (Kd03+HO). This body has neither the offensive odour or inflammability of the oxide ; but what is really astounding is the fact, that, although containing 56*27 per cent, of arsenic, with just the quantity of