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any of them except muriatic acid; nature, and it never assumes the state why then should it be essential to of muriatic acid, unless water or hythe constitution of that gaseous body? drogen be present.
There is a very remarkable gase- These unexpected results induced ous body first discovered by Scheele, Mr Davy to turn his attention to and called by him dephlogisticated the subject, and to endeavour to de. muriatic acid; afterwards examined prive this gaseous body of oxygen. with much care by Berthollet, and But all his endeavours were equally called by him oxymuriatic acid, be- unsuccessful. Well-burnt charcoal cause he considered it as a compound may be kept by means of the galvaof muriatic acid and oxygen. In nic battery, in a white heat in this this conclusion all scientific chemists gas, when well dried, without produagreed with him ; and it was the cing the smallest alteration on it. current opinion that the oxygen in When phosphorus is burnt in it a this substance was but loosely com- solid matter is obtained, which shews bined. Hence the reason of the very no indication of containing phosphopowerful manner in which it acts on rus, or phosphoric acid, and which, combustibles, setting them on fire, when placed in contact with ammoin many cases, by simple contact. niacal gas, absorbs it, and is convertThenard and Guy Lussac were indu- ed into a white, tasteless, insoluble ced to examine this gaseous body substance, having a strong resemanew, on the supposition that it would blance to silica in its properties. be easy to deprive it of its oxygen, When tin or any metal is burnt in and thus to obtain muriatic acid in a this gas, no indication appears of the state of purity, and proper for at formation of an oxide. In short, no tempting its decomposition. But oxide or acid can be separated from their efforts were not crowned with any of the products formed by means success. The results, however, which of this gas, unless we employ water in they obtained, were exceedingly cu- the first place to separate the excess rious and unexpected. They found of acid. When equal bulks of oxy. that no substance, not even charcoal, muriatic acid gas and hydrogen gas is capable of depriving oxymuriatic are mixed together in a close vessel, acid of oxygen, and reducing it to the no change takes place in the dark, state of muriatic acid, unless it con- but if they be exposed to the light tains water, or at least hydrogen, they gradually disappear, and muriawhich, in their opinion, combined tic acid gas is found in their place. with the oxygen of the acid, and If this mixture be exposed to the formed water. Hence the muriatic sun's rays, as was first observed by acid, whenever it was obtained, was Mr Dalton, and by Thenard and always in its usual state, and of course Guy Lussac, it takes fire, and ex. contaminated with water. Their ex. plodes; if the light be not strong, it periments led to the conclusion, that merely disappears rapidly, and asoxymuriatic acid, instead of being a sumes the form of muriatic acid
gas, loose compound, is one of the most which, if the experiment be made over intimate combinations in nature, and water, is instantly absorbed. The its two constituents cannot be sepa- diminution of bulk which takes place rated directly by any agent in our when this experiment is properly power. No degree of heat alters its made, does not exceed uth of the
whole. In all likelihood it would be ed when hyperoxymuriatic of potash less than this if the gases were quite is heated. Now this salt is formed pure and dry.
by causing a current of oxymuriatic Now it deserves attention, that the acid to pass through a solution of specific gravity of muriatic acid gas potash in water. is nearly the mean between that of It is obvious, that if Mr Dary's oxymuriatic acid gas and hydrogen theory prove correct, the term oxygas.
muriatic acid applied to this simple The specific gravity of oxymuria- substance is improper. Mr Davy tic acid gas is
2.470 has proposed to distinguish it by the Hydrogen gas
0.074 name chlorine, derived from the green
colour which it has when in the gaseThe mean of which is
1.272 ous state. Sp. gr. of muriatic acid . 1.278 If the nature of this substance, as
From this last fact, compared with suggested by Mr Davy, prove accuthe impossibility of decomposing rate, a very great alteration must be oxymuriatic acid, Mr Davy has drawn made in the presently received theory as a conclusion, that it is not a com- of chemistry. There will now be pound, as has hitherto been supposed, two simple supporters of combusbut a simple substance, and that mu- tion, namely, oxygen and chlorine, riatic acid is a compound of oxymu. and two distinct sets of compounds riatic acid and hydrogen united in formed by the union of each with equal bulks. This conclusion is re- combustible bodies. Muriatic acid markably supported by the compa- is a compound of chlorine and hyrison of the specific gravities of these drogen. "It combines likewise with different gases, and by the small sulphur and with phosphorus, and change of bulks which takes place forms bodies which are decomposed when a mixture of oxymuriatic and when placed in contact with water, hydrogen gases is changed into muand resolved into muriatic acid and riatic acid.
sulphuricand phosphoric acids. With This opinion of Mr Davy is very charcoal it does not combine. With nearly the same with the theory of Mr the metals it unites, and forms those Scheele, the original discoverer of compounds denominated butters by the oxymuriatic acid. Mr Davy has the old chemists, and improperly callsupported it with much ingenuity ed muriates by modern writers. Thus and sagacity, and by a great number what is called muriate of silver is a of new and curious experiments, in compound of chlorine and silver, two dissertations, which reach beyond fuming liquor of libavius, a comthe period of our history, and upon pound
of chlorine and tin ; and comwhich, therefore, we cannot enter at mon salt, a compound of chlorine and present. The subject cannot be con- sodium. Mr Davy proposes to dis. sidered as completely decided ; but, tinguish these compounds by the in our opinion, the weight of evidence names of the basis and the terminais on the side of Mr Davy's theory. tions ine or ane. Thus muriate of The most formidable objection, an ob. silver he calls argentane, muriate of jection which Mr Davy has not yet barytes, barytane, &c. removed in a satisfactory manner, is 12. Having detailed at sufficient the great quantity of oxygen obtain- length the iniportant discoveries of
Mr Davy, we must now turn our at. we must denote that of an atom of tention to Mr Dalton; one of the oxygen by 7. In like manner, ammost ingenious and industrious philo- monia is composed of an atom of hy. sophers of the present day. By the drogen, combined with an atom of introduction of a very simple but azote. Now it consists of 81.5 parts most important theory, he has con. by weight of azote, 18.5 parts of tributed very essentially to the im- hydrogen, or nearly of 4.5 azote; provement of chemical analysis, and and I hydrogen. Hence, if the to the accuracy of our notions re. weight of an atom of hydrogen be specting the constitution of compound represented by 1, that of an atom of bodies. According to him, when azote will be 4.5. In like manner, substances combine together, they from the analysis of carbonic acid, 'unite either to each other atom to an atom of charcoal will be found to atom, or one atom of the one com- weigh about 5, an atom of sulphur bines with a determinate number of weighs about 13, and an atom of atoms of the other. Water, for ex- phosphorus about 9. ample, is composed by the union of Now, knowing the relative weights one atom of oxygen with one atom of the different atoms, and the numof hydrogen. Now water is a com- ber of atoms which combine, it is pound of about 87.5 parts by weight easy to determine the composition of oxygen, and 12.5 of hydrogen, or of any compound, and likewise the of 7 parts of oxygen, and 1 of hy, relative weight of a particle of it. drogen. Hence we know that the The following table exhibits a few relative weights of an atom of each examples of these determinations, to of these bodies are to each other as 7 render them more familiar to the to 1. Therefore, if we denote the
reader: weight of an atom of hydrogen by 1,
Atoms. Atoms, 2. Water is composed of 1 oxygen and 1 hydrogen. A particle weighs 8 Ammonia 1 azote 1 hydrogen.
5.5 Carbonic acid
34 34 34
By the same mode of proceeding, we acid, give us the relative propor. may determine the relative weight of tions of the whole class of salts. an atom of the different metals. The protoxide of a metal is composed of
Constituents. one atom of the metal, and one atom of
Acid, Base. oxygen, the deutoxide of one atom of Thus sulphate of potash 34 metal, and two atoms of oxygen, and
69 so on. Thus, for example, if the
46 protoxide of lead be composed of
23 100 metal and 4 oxygen, it follows
maznesia 34 20 that the weight of an atom of lead is to that of an atom of oxygen as 100
Carbonate of potash 19 42 to 4. "Therefore, if we denote the
69 weight of an atom of oxygen by 7,
strontian 19 46 we must denote that of an atom of
liine 19 23 lead by 175. If the protoxide of
magnesia 19 20 copper be a compound of 100 metal and 11.5 oxygen, then the weight of The supersalts, or those which an atom of copper must be 60.8. contain an excess of acid, are formed
The same method furnishes us by the union of two particles of with the relative weight of a particle acid with one of base. Thus the of the earths and alkalies. For the super-sulphate of potash is composalts must be considered as compo- sed of 34x2=68 acid, +42 potash. sed of a particle of acid united to a On the other hand, the subsalts, or particle of base. Thus, sulphate of those which contain an excess of barytes is a compound of one particle base, are composed of two particles of sulphuric acid and one particle of of base united to one particle of acid. barytes. Now, by the most accurate Thus borax is composed of two par. analysis, it is composed of 33 parts ticles of soda and one particle of of sulphuric acid, and 67 barytes. boracic acid. Calcareous spar, and Hence, if the weight of a particle of all the other earthy combinations of sulphuric acid be denoted by 34, as carbonic acid, as they are commonly in the preceding table, that of a par- exhibited, are in reality subsalts, be. ticle of barytes must be denoted by ing combinations of two particles of 69. In the same way we may ob- earth with one of carbonic acid. An tain the weight of a particle of the additional dose of carbonic acid may earths and alkalies, as in the follow. be made to combine with these ing table :
earthy bases, but it easily makes its
escape again on account of its elasti. Potash
city. The nitrates constitute exSoda
ceptions to the general rule. They Barytes
are composed of two particles of Lime
acid and one particle of base united Magnesia
20 together. They are all of course
supersalts, though they do not red. Now these numbers, together with den vegetable blues. the weights of the particles of the The triple salts are formed by the
union of a particle of each of the Fourcroy and Vauquelin had ansalts which enters as a constituent. nounced also urate of ammonia as Thus tartrate of potash and soda, or a pretty common constituent ; but Rochelle salt, is composed of a par- Mr Brande has shewn that they were ticle of tartrate of potash united to a misled, partly by the urea, and partly particle of tartrate of soda.
by other alkaline salts, with which In the same way the metalline the uric acid was mixed. Urate of salts admit of analysis. They are ammonia, it would appear from his usually composed of a particle of experiments, is never found in urinary oxide united to a particle of acid. calculi. But to enter into particular details The calculi formed in the kidney would oblige us to extend this article are usually composed of uric acid; too far.
though, when they lodge in that orSuch is a short sketch of Mr Dal. gan, they are sometimes coated over ton's most curious and important with the phosphates. Calculi comtheory. It applies to all the com- posed of oxalate of lime are much pounds which have been analysed, rarer than any of the other species. especially to the salts, with such un- Mr Brande has shewn that the mecommon precision, that it is impossi. dicines usually prescribed do not act ble for the most sceptical chemist, as solvents, but often produce an adwho takes the trouble to examine ditional deposite of calculous matter ; the subject with sufficient care, to re- the alkalies diminish the proportion fuse his assent to it. For further de. of uric acid in urine ; but they tend tails respecting this theory, we refer to increase the deposite of the phosthe reader to Mr Dalton's New Sys- phates. Acids, on the other hand, tem of Chemical Philosophy, two promote the depositions of uric acid. volumes of which have been publish- 14. The phenomena of respiration od; or to the third volume of Dr have attracted the particular attention Thomson's System of Chemistry, 3d of chemists, ever since the discoveor 4th editions, where the subject is ries in pneumatic chemistry enabled stated at considerable length. them to ascertain the changes produ.
13. Some additions have been re- ced upon the air by drawing it into cently made to our knowledge of the lungs. Priestley, . Goodwin, animal substances, and of some of Menzies, Lavoisier, and Davy distin. the animal functions, which deserve to guished themselves particularly in be noticed. Mr William Brande has these inquiries. It was ascertained analysed a considerable number of that a portion of the oxygen of the, urinary calculi, which are deposited air drawn in disappeared, and that a in the Hunterian Museum in London, quantity of carbonic acid gas was and has corrected some errors of pre- found in its place ; but doubts were ceding experimenters, and contribu- entertained whether the bulk of the ted some additional facts of his own. air inhaled was diminished, whether
Preceding experimenters had de- the azote which it contained was dimi. tected a considerable number of sub. nished, and what was the proportion stances in urinary calculi ; the prin- of the carbonic acid formed to the cipal of which are uric acid, phos. oxygen withdrawn. A very accurate phate of lime, phosphate of magne. set of experiments has been made by sia and ammonia, oxalate of lime. Messrs Allen and Pepys to elucidate