inftant of their birth. A beam of light now bursts from all fides; opinions, the offspring of an extravagant imagination, are' configned to oblivion; and elegance and ftability are given to the fabric. But to collect facts is the labour of the dull compiler; to introduce order. and symmetry is the work of genius and discernment.

We are led into these reflections by the perufal of the treatise before us. Our expectations are indeed difappointed. The production is below mediocrity. To originality of matter, to clearness of method, to beauty of order, it has no pretenfions. The language is flovenly and inaccurate, and the arrangement is uncommonly confufed. The author plumes him-felf in being able to comprise the whole fyftem of chemistry in a fingle volume. But fmall is the merit of fo paltry ant abridgment.

The work is divided into two books: the first confiders general chemistry, the second particular chemistry. The author's definition of chemistry conveys no idea whatever: As a fcience, its object,' fays he, is to estimate and account the 'changes produced in bodies by motions of their parts, which are too minute to affect the fenfes individually.' It is feldom that we meet with a sentence fo obfcure. Does he mean that the parts of bodies are too minute to affect the senses; or that their motions are too minute to affect the fenfes? To what does the word individually refer? Is it meant that one fenfe alone receives the impreffion; or that one part, or one motion, produces the fenfation. If the fentence has any meaning at all, it admits of four different applications. Befides, the word eflimate, in the prefent cafe, conveys no idea.-The author proceeds, in a curfory manner, to mention analyfis, fynthesis, elective attractions, &c. At once we are hurried into the midst of the science; and the effects of heat are stated before the term is explained. Heat expands folids, then renders them fluid, and afterwards • converts them into vapour; and these changes fucceed each other according as the intenfity of the heat is rendered greater.' This is, no doubt, very laconic; but unfortunately the last clause of the fentence is nonfenfe.-In the fecond chapter, the author begins more deliberately. He makes the common remark, that the word heat is employed either to denote the fenfation itself, or the cause of that fenfation. The effect is fuppofed by fome to be' produced by the internal vibration of the particles of bodies; by others it is imagined that the agent is a certain fubtle fluid which is diffused through the univerfe. Some bodies are more easily heated than others in the fame fituation, and are therefore termed better conductors of heat. Whatever be the cause of heat, its general effect is to enlarge the dimenfions of bodies;

and

and this expansion is found to be nearly proportional to the additions of heat that are made. It has a tendency to an equal diffusion; but it does not follow that all bodies of the fame temperature contain it in equal quantity; for fome are more fufceptible of its effects than others. Hence the diftinction into abfolute and relative heat. The denfities of heat in different bodies in a fimilar exposure, are termed their capacities for heat. The capacity may be estimated from the change of temperature observed in mechanical mixture. Some philofophers have afcertained it by the quantities of ice, which different bodies, at the fame temperature, were able to melt. Water has a greater capacity for heat than ice, and steam a ftill greater than water. Hence arife the effects of evaporation and frigorific mixtures.

In Chap. III. Mr. Nicholfon treats particularly of the thermometer, and gives directions for the conftruction and examination of it, and concludes with the rules for converting the degrees of Farenheit's into thofe of Reaumur and Celfius. He next explains, in a curfory manner, the various operations of chemistry; calcination, fufion, cementation, digeftion, diftillation, &c. and gives a fhort description of the more common apparatus. Our author then confiders the mode of operating upon elastic fluids, defcribes the eudiometer, and Dr. Nooth's elegant apparatus for impregnating water, and ftates the improvements which have been made in collecting the aerial products in diftillation.

I

of

The next chapter is allotted to the confideration of weights and balances; a subject of great importance in nice chemical experiments. The delicacy of a balance is indicated by the flowness of the vibrations of the beam. The accuracy which has been introduced is quite aftonifhing. Mr. Bolton had a balance, which, when loaded with a pound, would turn with the tenth of a grain. One made for Dr. George Fordyce is affected by the the weight; and the balance lately made by Mr. Ramsden for the Royal Society can ascertain a weight to the Seven millionth part! The first part of the work concludes with fome remarks upon the inertia of matter, gravity, elective attraction, folutior, cryftallifation, &c. The author feems fond of the filly notion of the polarity of particles.

384,000

Mr. Nicholson proceeds, in the fecond book, to confider particular chemistry. He fpeaks of light as if the doctrine were founded entirely upon conjecture. It is generally • taken for granted,' fays he, that light is a fubftance, or an emanation of particles of prodigious minuteness, which are projected in right lines, with extreme velocity, from lumi< nous bodies; and that they are repelled from all bodies at Y ❝ certain ENG. REV. VOL. XV. MAY 1790.

< certain distances, and at lefs diftances attracted, fo as to pro ⚫duce all the effects of reflection, refraction, and inflection, in the rays they compofe.' What a strange inconfiftent medley of words and ideas! He then flightly mentions the notion affixed by the chemifts to the word phlogifton, and Mr. Kirwan's fuppofition that it is the fame with hydrogenous gas. He next confiders combuftion, the abforption of oxygen gas, the production of this gas, the nitrous teft, the hydrogenous gas, the compofition of water, and the effects of the eoliple. After this rapid view of the aerial fluids, he defcends to treat of the primitive earths. He confiders the alkalis, relates the process for the manufacture of glass and foap, and mentions the general properties of the mineral, vegetable, and animal acids. Mr. Scheele defcribed a process for extracting foffil alkali from sea falt. Mr. Turner triturates litharge with water and half its weight of common falt, till it affumes a white colour, and then allows the mixture to ftand for fome hours. The alkali is dif engaged, and the marine acid unites to the calx of lead, and forms a yellowish green pigment, the fale of which is the principal object of the manufacturer. He next surveys the metals; mentions the divifion into perfect and imperfect, their calcination, cryftallifation, folution, &c. and the oppofite theories which have been formed on thefe fubjects.

Mr. Nicholson now returns to examine more minutely what he had before flightly touched. He details the properties of vitriolic acid and fulphur, and their various changes and combinations. This acid is generally obtained by burning a mixture of eight parts of fulphur with one of nitre, in a large veffel lined with lead, and containing a small portion of water to abforb the fumes.-He next confiders a very interefting fubject, that of the nitrous acid; the formation of nitre beds, the extraction and purification of the falt, its deflagration and detonation, the compofition of gunpowder, the pulvis fulminans, &c. the diftillation of the acid, its formation, its effect upon animal fubftances and the effential oils; and flightly explains the oppofite theories which have been offered. The marine acid occupies the next chapter. The fea contains, he fays, between the tropics, from an eighth to an eleventh of its weight of falt. This is a miftake; for in no part of the world does the quantity exceed one twentieth. He relates the various methods of extracting the falt, and of cryftallifing it. The diftillation of the acid, and the various compounds that it forms, are next confidered. The oxygenated marine acid is of a fingular nature; and its property of inftantly deftroying colour, has been directed with advantage to the bleaching of wax and linen. The power of aqua regia to disfolve gold is probably derived from the extemporaneous pro

7

duction

duction of oxygenated marine acid. Our attention is next turned to the carbonic gas, and thofe fubftances and proceffes which contribute to its formation, the calcareous matters, fermentation, and the combuftion of charcoal. Its acidulating quality, and its combination with earths and alkalis, are mentioned. The acid of borax comes next to be confidered; its production, its purification, its analyfis, its properties. The acid of amber has lately been examined, but its properties are not remarkable.

Mr. Nicholson next treats of the phofphoric acid, a subject on which so much light has lately been thrown. It abounds in animal fubftances, it occurs in the cruciform plants, and it is even found in the mineral kingdom. It is fometimes combined with the ores of lead; and to iron it communicates the cold-fhort quality; an unfortunate circumstance for the manufacturers of this country. Both phofphorus and its acid are now obtained with eafe from bone afhes. The acid is always formed by the union of oxygen with the phosphorus, and may be procured in greater purity by the inflammation of the phofphorus, by the fpontaneous decompofition arifing from expofure, or by the action of nitrous acid. Phofphorus diffolves in oils and ardent fpirits, and communicates to them a luminous appearance. The folution in fome of the effential oils has the property of fpontaneous inflammation, when expofed to the air. A ftick of phofphorus, plunged into the folutions of gold, filver, copper, and other metals, is gradually covered with a brilliant metallic fheath. The phosphoric acid combines with all the alkalis. Other acids have lately been examined, the theory of which is scarcely yet afcertained. The acids of arfenic, molybdena, and turgoten, obtained from the ores.

Mr. Nicholson then proceeds to the confideration of the metals. The malleability and ductility of gold is quite astonishing. It is unalterable in the ftrongeft heat of our furnaces. It is, however, volatilifed in the focus of powerful burning-glaffes, and partially calcined. The electric explofion converts it into a purple calx. Gold is foluble alone in aqua regia and oxygenated muriatic acid. By a careful evaporation the folution yields fine crystals of a topaz colour. It is precipitated by the earths and alkalis, and even by the addition of martial vitriol, and forms a yellowish or purplish powder. The precipitate made by volatile alkali or fal ammoniac is termed aurum fulminans, because, when gently heated, it explodes with aftonishing violence. The volatile alkali, which unites to the calx, is fuddenly decomposed; the oxygen combines with the hydrogenous gas and forms water, while the azotic gas is inftantly extricated. Hence the vitriolic acid, oils, æther, &c. which detach the volatile alkali, destroy the fulminating quality. If gold be precipitated

Y 2

precipitated from aqua regia by means of tin, we obtain the purple powder of Caffius, which is ufed as an enamel. Gold is not acted upon by nitre or the alkalis. It diffolves, however, in the liver of fulphur. It combines moft readily with mercury. Hence the process of water-gilding.-Silver comes next to be confidered. It is fixed in the heat of common furnaces; but, expofed in the focus of a powerful lens, it fumes and vitrifies. It is tarnished by the influence of the air; and the scales' which are formed, during a course of years, upon filver images, are found to be a compound of that metal with fulphur. Silver diffolves in all the mineral acids. The folution in nitrous acid yields thin cryftals, which are called lunar nitre; and these, when fufed, form lunar cauftic. The affufion of marine acid produces luna cornea, which is difficultly foluble, and is thrown down. Heated with fixed alkali, it yields the pureft filver. A curious difcovery has lately been made by the ingenious M. Berthollet. He diffolves pure filver in pale nitrous acid, and precipitates it from the folution by the addition of lime-water. He dries the calx by expofing it to the air for three days. He next stirs it in a folution of cauftic volatile alkali till it becomes a black powder; he then decants the fluid, and leaves it to dry. This is fulminating filver. The experiment requires to be conducted with the utmoft caution. The flighteft agitation occafions an inftantaneous and dreadful explofion. The theory is the fame with that of fulminating gold. Mercury feparates filver from its folutions extremely flowly. The precipitate affumes fanciful forms, and fometimes refembles the ramifications of a tree; and hence is termed by the alchemifts arbor Diana.-The new metal, platina, is next confidered; it is the denfeft of all the metals. It has, in common with iron, the fingular property i welding. It is precipitated from the folution in aqua regia by fal ammoniac, which diftinguishes it from the other metals. It is not affected by the Pruffian alkali; and this circumftance is the foundation of the method of feparating it from iron, with which it is commonly combined. Platina forms with copper a compound that admits of a fine polifh, and is not fubject to tarnish; and hence it has been ufed for the mirrors of reflecting telescopes. Mr. Nicholfon next mentions the properties of mercury, its various compounds and preparations. Lead is the next in order. It is precipitated from its folutions by the liver of sulphur. If fead be heated with charcoal and phofphoric acid, the acid is converted into phofphorus, and combines with the metal. The compound, in its appearance, refembles lead. By the affiftance of heat, lead decompofes fal ammoniac, and difengages the volatile alkali. Litharge, fufed with common falt, unites to the marine acid, and forms a yellow pigment. A mixture of eight

parts