Experiments and Observations on the Following Subjects E-Book

Thomas Henry

• Herausgeber: Science & Technology Publishing
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 93

Veröffentlichungsjahr: 2025

Beschreibung

Experiments and Observations on the Following Subjects is a seminal scientific work by John Smeaton, first published in the 18th century. This comprehensive volume presents a detailed account of Smeaton’s pioneering research and practical experiments in the fields of engineering, physics, and mechanics. The book is divided into several sections, each focusing on a specific subject of inquiry, including the power of water and wind mills, the strength and properties of various materials, and the construction and efficiency of engines and machinery. Smeaton meticulously documents his experimental methods, observations, and results, providing readers with clear explanations and illustrations that enhance understanding. He explores the effects of different variables on mechanical performance, such as the impact of water flow on mill wheels, the resistance of air and water, and the comparative advantages of different engine designs. The work also delves into the principles of hydraulics, pneumatics, and the application of scientific knowledge to practical engineering problems. Throughout the book, Smeaton emphasizes the importance of empirical evidence and careful measurement, setting a standard for scientific inquiry in engineering. His observations laid the groundwork for future advancements in civil and mechanical engineering, influencing the design of bridges, lighthouses, and other critical infrastructure. Experiments and Observations on the Following Subjects remains a valuable historical document, offering insight into the early development of experimental science and the innovative spirit of the Industrial Revolution.

Leseprobe

EXPERIMENTSAND OBSERVATIONS

ON THE FOLLOWING SUBJECTS;

1.

On the preparation, calcination, and medicinal uses of

Magnesia Alba

.

4.

On Various

Absorbents

, as promoting or retarding putrefaction.

2.

On the Solvent Qualities of

Calcined Magnesia

.

5.

On the comparative Antiseptic Powers of

Vegetable Infusions

prepared with

Lime

, &c.

3.

On the variety in the Solvent Powers of

Quick-Lime

, when used in different quantities.

6.

On the Sweetening Properties of

Fixed Air

.

BYTHOMAS HENRY, Apothecary.

Utut tamen se res habeat, ego bona saltem fide tradam quæ hactenus rescivi omnia.

Sydenham.

LONDON: Printed for Joseph Johnson, No. 72, St. Paul's Church-Yard. MDCCLXXIII.

TOThomas Percival, M.D. F.R.S. & S.A.

Dear Sir,

WHEN I reflect how much the friendship with which you have favoured me has contributed to my happiness; that from you has been imbibed a considerable share of the small taste I possess for experimental inquiries; and that to your skilful and affectionate treatment I am greatly indebted even for the health I enjoy; it is impossible to hesitate a moment in the choice of a patron: gratitude and esteem direct me to inscribe this Treatise to you, and I chearfully obey their dictates. If to these any additional motive had been wanting, I should have received it from your having been an evidence to the result of many of the experiments related in the following pages.

That your own health may long enable you to continue exemplarily useful to your friends and to the public, is the sincere and ardent wish of,

Dear Sir, Your truly affectionateand very humble Servant,

Thomas Henry.

Manchester, 18th Jan. 1773.

THE PREFACE.

A RIGHT composition of the several articles used in medicine, is of so much importance to the practice of it, that every attempt to improve or ascertain the method of preparing them, cannot fail of a candid reception from the public.

Though great advancement has been made within these few years in chemical pharmacy, by the labours of the very ingenious Dr. Lewis, and some other writers on chemistry and the materia medica, there is still a wide field left for improvement. It is to be wished that Apothecaries, to whose province researches of this kind more peculiarly belong, and many of whom are well qualified by a liberal education to pursue them with advantage, would give their attention to these material interests of the art: for while the several professors of medicine and of surgery, are most laudably and assiduously employed in adding to the enlargement of these sciences, why should the sons of pharmacy remain supinely inactive, and leave every thing towards the improvement of their profession to be performed by the members of the elder branch of physic, instead of contributing their share to its support? as if tacitly acknowledging themselves unequal to the task, and thereby incurring the too general, though unmerited, imputation of want of knowledge and skill in their department.

The first part of the ensuing Treatise, which relates an improved method of preparing Magnesia Alba, has been communicated to the College of Physicians; and that learned body have done the author the honour to insert it in the second volume of theirTRANSACTIONS. It is here reprinted as a proper introduction to the subsequent pages.

The calcination of Magnesia is not a new process[a]; but, as in this state it is a medicine not much introduced into practice, perhaps a few hints may be suggested, in regard to its medicinal and pharmaceutical properties, which are not generally known; and it is hoped that some useful information may be communicated relative to the various action of absorbent medicines on the bile.

In the succeeding chapters, it is attempted to determine how far, and in what proportion, lime promotes the solution of vegetable astringents, and other drugs in water; and whether the action of antiseptic medicines, thus dissolved, be in any degree impaired or increased by this mode of obtaining tinctures from them.

In endeavouring to contribute to the determination of the question, whether fixed air has the power of restoring sweetness to putrid substances, the Author may at first sight appear to have transgressed his proper limits; but, as fixed air, if possessed of this property, is likely to be a valuable acquisition to the materia medica, he flatters himself he shall incur no censure by the attempt.

THE CONTENTS.

CHAP. I.

Page

An Account of an improved Method of preparing Magnesia Alba.

1

CHAP. II.

Miscellaneous Observations.

12

CHAP. III.

On the Medicinal Properties of Magnesia Alba.

25

CHAP. IV.

On the Calcination of Magnesia Alba.

39

CHAP. V.

On the Medicinal Virtues of Calcined Magnesia.

48

CHAP. VI.

On the Action of various Absorbents, as promoting or retarding putrefaction.

58

CHAP. VII.

On the Solvent Qualities of Calcined Magnesia.

80

CHAP. VIII.

On the various Solvent Powers of Quick Lime in different Quantities.

88

CHAP. IX.

On the comparative Antiseptic Powers of Vegetable Infusions prepared with Lime, &c.

105

CHAP. X.

On the Sweetening Properties of Fixed Air.

114

CHAP. XI.

A Review of the general Conclusions deducible from the foregoing Observations and Experiments.

135

AN APPENDIX

143

ERRATA.

Page 8, line 14, after quantity read of water.Page 10, line 18, for interrupt read intercept.Page 13, line 1, read is there said.Page 16, line 1, read the other absorbents.Page 29, note, line 4 from the bottom, for albuminis read aluminis.Page 31, line 4, for patients read parents.Page 83, line 9, after elegant read green.Page 126, line 3, erase the comma after smell.Page 127, line 3, place a comma instead of the semicolon.

CHAP. I.

An account of an improved method of preparing MAGNESIA ALBA.

ALTHOUGH Magnesia Alba is a medicine which has been in general use for many years, yet the proper mode of making it is very little known. Our pharmacopæia affords us no information about it; and the formula which is given by the Edinburgh College, as well as that with which the ingenious Doctor Black[b] has favoured us, is deficient in several circumstances. Hence the preparation of pure Magnesia has been confined to very few persons, who have preferred the emolument they have received by keeping their method secret, to the more diffusive utility of which a publication of it would have been productive.[c] I therefore beg leave to lay before the public a process for the preparation of Magnesia, by which it will be in the power of every Apothecary to make it himself, in all respects equal to that which is sold by those who conceal their method.

I am the more strongly induced to make this communication, because the Magnesia which is generally to be found in the shops, is either extremely coarse and ill prepared, or, which is still worse, sophisticated with calcareous substances, differing greatly from true Magnesia. I have been assured by some Physicians, that they have met with it mixed with chalk, and even with lime, and I have sometimes seen it so adulterated: a fraud of very dangerous tendency, as this powder is so frequently administered to very young infants, and to adults of tender bowels and costive habits.

This medicine was originally prepared abroad, from the liquor called the mother of nitre, which is composed of a light earth united with an acid; and these being separated, either by a strong fire, or by the addition of an alkali, the powder was washed in water, and obtained the name of Magnesia Alba. Hoffman afterwards prepared it from the bittern remaining after the crystallization of sea salt, which he found to be similar to the mother of nitre. And the factitious Epsom salt being prepared from this bittern, and evidently composed of Magnesia and the vitriolic acid, Dr. Black, who has favoured the world with a number of very valuable experiments on this subject, made use of this salt with success for the same purpose.

Happening some years ago to live in the neighbourhood of a gentleman who has long been celebrated as the preparer of the most genuine Magnesia, and never having been able myself to make Magnesia comparable to his, by the commonly known methods, I was desirous of gaining some intelligence as to his process, and was at last so fortunate as to obtain some useful hints.

I availed myself of these, and after repeated trials, produced Magnesia equally pure, white, tasteless, light and impalpable with that of Mr. Glass; nay sometimes that of my own preparing has been superiour to his, and in one respect has generally the advantage of it, namely, that mine is not so stiff when dried, and may be reduced to the finest powder by simple pressure; whereas his requires some degree of trituration to break the lumps effectually; which I imagine may be owing to his pursuing Dr. Black's method of drying it, by straining and pressing out the water through a cloth.

The following is the manner of preparing it, which I have found successful.

Dissolve any quantity of sal catharticus amarus, commonly called Epsom salts, in its own weight of water; filter the liquor, and add to it by degrees a filtrated solution of pearl ashes in an equal quantity of water, stirring them gently until the mixed liquors have acquired the appearance of a complete coagulum: then cease adding any more of the alkaline lixivium; and, having diluted the precipitate, and mixed it intimately with a small quantity of hot water, immediately throw the mixture into a large vessel of boiling water. Keep it boiling for a quarter of an hour, then take it out, and put it into glazed earthen vessels. As soon as the powder has subsided, and before the water be quite cold, pour it off, and add a fresh quantity of boiling water: repeat these ablutions with several parcels of hot water, till the liquor has entirely lost its saline taste. Then let it be so agitated as to suspend the finer parts of the powder; in which state decant it into other vessels, and having separated the water from the Magnesia by inclination, put it on large chalk stones, till a considerable part of the humidity be absorbed. Then wrap it up in sheets of white paper, and dry it before the fire. Pour hot water on the remaining powder, stir it, decant it in its turbid state, and separate the Magnesia from the water as before. By these means, the whole, or most of it, will be reduced to an equal degree of fineness.

The separation of the Magnesia will be promoted by heating the saline lixivia before they are mixed; and the larger the quantity or water into which the precipitated powder is cast, the more speedily and perfectly will the vitriolated tartar, which is formed by the alkali of the sal catharticus, be washed off. Dr. Black directs that three or four times the quantity of water, to that of the solutions, should be added; but this I have found