Elements of Chemistry Part 24

Lime lime.

Barytes barytes.

Magnesia magnesia.

Oxyd of zinc zinc.

iron iron.

manganese manganese.

cobalt cobalt.

nickel nickel.

lead lead.

tin tin.

copper copper.

bis.m.u.th bis.m.u.th.

antimony antimony.

a.r.s.enic a.r.s.enic.

silver silver.

mercury mercury.

gold gold.

platina platina.

_Note._---All these were unknown to former chemists.--A.

_Observations upon the Prussic Acid, and its Combinations._

As the experiments which have been made hitherto upon this acid seem still to leave a considerable degree of uncertainty with regard to its nature, I shall not enlarge upon its properties, and the means of procuring it pure and dissengaged from combination. It combines with iron, to which it communicates a blue colour, and is equally susceptible of entering into combination with most of the other metals, which are precipitated from it by the alkalies, ammoniac, and lime, in consequence of greater affinity. The Prussic radical, from the experiments of Scheele, and especially from those of Mr Berthollet, seems composed of charcoal and azote; hence it is an acid with a double base. The phosphorus which has been found combined with it appears, from the experiments of Mr Ha.s.senfratz, to be only accidental.

Although this acid combines with alkalies, earths, and metals, in the same way with other acids, it possesses only some of the properties we have been in use to attribute to acids, and it may consequently be improperly ranked here in the cla.s.s of acids; but, as I have already observed, it is difficult to form a decided opinion upon the nature of this substance until the subject has been farther elucidated by a greater number of experiments.

FOOTNOTES:

[36] See Memoirs of the Academy for 1776, p. 671. and for 1778, p.

535,--A.

[37] See Part I. Chap. XI. upon this subject.--A.

[38] See Part I. Chap. XI. upon the application of these names according to the proportions of the two ingredients.--A

[39] See Part I. Chap. XII. upon this subject.--A.

[40] Those who wish to see what has been said upon this great chemical question by Messrs de Morveau, Berthollet, De Fourcroy, and myself, may consult our translation of Mr Kirwan's Essay upon Phlogiston.--A.

[41] Saltpetre is likewise procured in large quant.i.ties by lixiviating the natural soil in some parts of Bengal, and of the Russian Ukrain.--E.

[42] Commonly called _Derbys.h.i.+re spars_.--E.

[43] I have not added the Table of these combinations, as the order of their affinity is entirely unknown; they are called _molybdats of argil_, _antimony_, _potash_, &c.--E.

[44] This acid was discovered by Mr Scheele, to whom chemistry is indebted for the discovery of several other acids.--A.

[45] I have omitted the Table, as the order of affinity is unknown, and is given by Mr Lavoisier only in alphabetical order. All the combinations of malic acid with salifiable bases, which are named _malats_, were unknown to the ancient chemists.--E.

[46] The order of affinity of the salifiable bases with this acid is. .h.i.therto unknown. Mr Lavoisier, from its similarity to pyro-lignous acid, supposes the order to be the same in both; but, as this is not ascertained by experiment, the table is omitted. All these combinations, called _Pyro-tartarites_, were unknown till lately--E.

[47] Savans Etrangers, Vol. III.

[48] These combinations are called Benzoats of Lime, Potash, Zinc, &c.; but, as the order of affinity is unknown, the alphabetical table is omitted, as unnecessary.--E.

[49] These combinations, which were all unknown to the ancients, are called Camphorats. The table is omitted, as being only in alphabetical order.--E.

[50] These combinations, which are called Gallats, were all unknown to the ancients; and the order of their affinity is not hitherto established.--A.

[51] These combinations are called Lactats; they were all unknown to the ancient chemists, and their affinities have not yet been ascertained.--A.

[52] These combinations named Bombats were unknown to the ancient chemists; and the affinities of the salifiable bases with the bombic acid are hitherto undetermined.--A.

[53] All the combinations of this acid, should it finally turn out to be one, were unknown to the ancient chemists, and its affinities with the salifiable bases have not been hitherto determined.--A.

PART III.

Description of the Instruments and Operations of Chemistry.

INTRODUCTION.

In the two former parts of this work I designedly avoided being particular in describing the manual operations of chemistry, because I had found from experience, that, in a work appropriated to reasoning, minute descriptions of processes and of plates interrupt the chain of ideas, and render the attention necessary both difficult and tedious to the reader. On the other hand, if I had confined myself to the summary descriptions. .h.i.therto given, beginners could have only acquired very vague conceptions of practical chemistry from my work, and must have wanted both confidence and interest in operations they could neither repeat nor thoroughly comprehend. This want could not have been supplied from books; for, besides that there are not any which describe the modern instruments and experiments sufficiently at large, any work that could have been consulted would have presented these things under a very different order of arrangement, and in a different chemical language, which must greatly tend to injure the main object of my performance.

Influenced by these motives, I determined to reserve, for a third part of my work, a summary description of all the instruments and manipulations relative to elementary chemistry. I considered it as better placed at the end, rather than at the beginning of the book, because I must have been obliged to suppose the reader acquainted with circ.u.mstances which a beginner cannot know, and must therefore have read the elementary part to become acquainted with. The whole of this third part may therefore be considered as resembling the explanations of plates which are usually placed at the end of academic memoirs, that they may not interrupt the connection of the text by lengthened description. Though I have taken great pains to render this part clear and methodical, and have not omitted any essential instrument or apparatus, I am far from pretending by it to set aside the necessity of attendance upon lectures and laboratories, for such as wish to acquire accurate knowledge of the science of chemistry. These should familiarise themselves to the employment of apparatus, and to the performance of experiments by actual experience. _Nihil est in intellectu quod non prius fuerit in sensu_, the motto which the celebrated Rouelle caused to be painted in large characters in a conspicuous part of his laboratory, is an important truth never to be lost sight of either by teachers or students of chemistry.

Chemical operations may be naturally divided into several cla.s.ses, according to the purposes they are intended for performing. Some may be considered as purely mechanical, such as the determination of the weight and bulk of bodies, trituration, levigation, searching, was.h.i.+ng, filtration, &c. Others may be considered as real chemical operations, because they are performed by means of chemical powers and agents; such are solution, fusion, &c. Some of these are intended for separating the elements of bodies from each other, some for reuniting these elements together; and some, as combustion, produce both these effects during the same process.

Without rigorously endeavouring to follow the above method, I mean to give a detail of the chemical operations in such order of arrangement as seemed best calculated for conveying instruction. I shall be more particular in describing the apparatus connected with modern chemistry, because these are hitherto little known by men who have devoted much of their time to chemistry, and even by many professors of the science.

CHAP. I.

_Of the Instruments necessary for determining the Absolute and Specific Gravities of Solid and Liquid Bodies._

The best method hitherto known for determining the quant.i.ties of substances submitted to chemical experiment, or resulting from them, is by means of an accurately constructed beam and scales, with properly regulated weights, which well known operation is called _weighing_. The denomination and quant.i.ty of the weights used as an unit or standard for this purpose are extremely arbitrary, and vary not only in different kingdoms, but even in different provinces of the same kingdom, and in different cities of the same province. This variation is of infinite consequence to be well understood in commerce and in the arts; but, in chemistry, it is of no moment what particular denomination of weight be employed, provided the results of experiments be expressed in convenient fractions of the same denomination. For this purpose, until all the weights used in society be reduced to the same standard, it will be sufficient for chemists in different parts to use the common pound of their own country as the unit or standard, and to express all its fractional parts in decimals, instead of the arbitrary divisions now in use. By this means the chemists of all countries will be thoroughly understood by each other, as, although the absolute weights of the ingredients and products cannot be known, they will readily, and without calculation, be able to determine the relative proportions of these to each other with the utmost accuracy; so that in this way we shall be possessed of an universal language for this part of chemistry.

With this view I have long projected to have the pound divided into decimal fractions, and I have of late succeeded through the a.s.sistance of Mr Fourche balance-maker at Paris, who has executed it for me with great accuracy and judgment. I recommend to all who carry on experiments to procure similar divisions of the pound, which they will find both easy and simple in its application, with a very small knowledge of decimal fractions[54].