1.1391 20.37 27.07 26.28

1.0114 1.70 2.26

2.19

1.0095 1.41 1.88 1.0076 1.13 1.50 1.46

1.82

1.0037 0.56 0.752 0.73 1.0019 0.28 0.376 0.365 1.000 0.00 0.000 0.000

The fundamental density of the acid of the preceding table is 1.1920, which is as strong as it is comfortable to make or to use in chemical researches. To find the quantity of real acid in that possessed of greater density, we have only to dilute it with a known proportion of water, till it come within the range of the table. The short memoir in the Annals for November, contains the logarithmic series corresponding to the range of densities and acid strengths; but for all ordinary purposes the following simple rule will serve: Multiply the decimal part of the number denoting the specific gravity by 147, the product will be very nearly the per-centage of dry acid, or by 197 when we wish to know the per-centage of the acid

2. The specific gravity is 1.096; the quantity of acid gas is sought.

0.096 × 197 = 18.9. By the table it is 18.8.

According to the new doctrine of Sir H. Davy there is no such substance as the dry acid; and therefore in a theoretical point of view, the column containing it might have been expunged. But for practical purposes it is very useful, for it shows directly the increase of weight which any alkaline or earthy base will acquire, by combining with the liquid acid. Thus, if we unite 100 grs. of liquid acid sp. gravity 1.1134 with quicklime, we see that the base will, on evaporation to dryness, be heavier by 16.7 grains. We would require a little calculation to determine this amount from the other columns. We have seen it stated that water, in absorbing 480 times its bulk of the acid gas, becomes of specific gravity 1.2109. If we compute from these data the increase of its bulk, we shall find it equal to 1.42, or, nearly one and a half the volume of the water. 481 parts occupy only 1.42 in bulk, a condensation of about 340 into one. The consequence of this approximation of the particles, is the evolution of their latent heat; and accordingly the heat produced in the condensation of the gas is so great that it melts ice almost as rapidly as the steam of boiling water does. Hence also in passing the gas from the beak of a retort into a Woulfe's apparatus containing water to be impregnated, it is necessary to surround the bottles with cold water or ice, if we wish a considerable condensation.

Dr. Thomson, in the second volume of his System of Chemistry, 5th edition, has committed some curious mistakes in treating of the aqueous combination of muriatic acid gas. He says, "A cubic inch of water at the temperature of 60°, barometer 29.4, absorbs 515 cubic inches of muriatic acid gas, which is equivalent to 308 grains nearly. Hence water thus impregnated contains 0.548, or more than half of its weight of muriatic acid, in the same state of purity, as when gaseous. I caused a current of gas to pass through water, till it refused to absorb any more. The specific gravity of the acid thus obtained was 1.203. If we suppose that the water in this experiment absorbed as much gas as in the last, it will follow from it that 6 parts of water, being saturated with this gas, expanded so as to occupy very nearly the bulk of 11 parts; but in all my trials the expansion was only to 9 parts. This would indicate a specific gravity of 1.477; yet upon actually trying water thus saturated, its specific gravity was only 1.203. Is this difference owing to the gas that escapes during the taking of the specific gravity?" page 232.

We are here presented with a puzzle for the chemical student; and an instructive example, when one takes the trouble of unravelling the hank, of a contest between experimental results and false computation. Granting all the experimental statements to be exact, none of the consequences follow. For, in the first place, 515 cubic inches of muriatic acid gas do not weigh 308 grains nearly, but only 201 grains; and hence, secondly, his liquid acid could contain at utmost only 0.443 of its weight of gas, instead of 0.548; and, in the third place, the calculated enlargement of bulk is 1.5, or from 6 to 9, and not to 11; so that the quere with which he concludes is superseded. But another quere may here be started, about the experimental results themselves. Dr. Thomson says, that a cubic inch of water absorbs 515 cubic inches of gas, and acquires the specific gravity by experiment of 1.203. Sir H. Davy states, that a cubic inch of water absorbs about 480 cubic

inches of gas, and forms a liquid of specific gravity 1.2109. Now it is remarkable that Dr. Thomson's additional condensation of 35 inches of gas gives a less specific gravity than we have in the stronger acid of Sir H. Davy.

But farther, the table constructed by Sir H. and E. Davy presents for its fundamental density the number 1.20 of Dr. Thomson. Now this particular acid of 1.20 was carefully analyzed by nitrate of silver, and is stated by Sir H. to contain in 100 grains 40.8 grains of condensed gas. Of course we have a remainder of 59.2 grains of water. 40.8 gr. of gas have a volume at the ordinary pressure and temperature of 104 cubic inches, reckoning the weight of 100 cubic inches to be 39.162 gr. with Dr. Thomson. And as 59.2 gr. of water have absorbed 104 cubic inches, we have the following proportion, 59.2: 104:: 252.5: 443. Thus a cubic inch has condensed only 443 cubic inches, instead of 515. as by Dr. Thomson. And whatever error may be supposed to be in their table, it is but minute, and undoubtedly does not consist in underrating the quan. tity of condensed gas.

By uniting the base of this gas with silver, and also with potassium, Berzelius has lately determined the prime equivalent of muriatic acid to be 3.4261, whence chlorine comes out 4.4261, and muriatic gas 4.4261 + 0.125 (the prime of hydrogen) = 4.5511. But if we take 1.278 as the specific gravity of this acid gas, then the specific gravity of chlorine will be twice that number, minus the specific gravity of hydrogen, or (1.278 × 2) -0.0694 = 2.4866; and as chlorine and hydrogen unite volume to volume, then the relation of the prime of chlorine will 2.4866 0.0694

be to that of hydrogen =

= 35.83.

If we divide this by 8, we shall have 4.48, to represent the prime equivalent of chlorine, and 4.48 +0.125 = 4.605 for that of muriatic acid gas.

But if we call the specific gravity of dry muriatic acid gas 1.2590, as Sir H. Davy says it should be by calculation, then the sp. gravity of chlorine becomes 2.4486, and its prime 4.42, a number agreeing nearly with the latest researches of Berzelius.

Muriatic acid, from its composition, has been termed by M. Gay-Lussac the hydrochloric acid; a name objected to, on good grounds, by Sir H. Davy. It was prepared by the older chemists in a very rude manner, and was called by them spirit of salt.*

In the ancient method, common salt was

previously decrepitated, then ground with dried clay, and kneaded or wrought

with water to a moderately stiff consistence, after which it was divided into balls of the size of a pigeon's egg: these balls, being previously well dried, were put into a retort, so as to fill the vessel two-thirds full; distillation being then proceeded upon, the muriatic acid came over when the heat was raised to ignition. In this process eight or ten parts of clay to one of salt are to be used. The retort must be of stone-ware well coated, and the furnace must be of that kind called reverberatory.

It was formerly thought, that the salt was merely divided in this operation by the clay, and on this account more readily gave out its acid; but there can be little doubt, that the effect is produced by the siliceous earth, which abounds in large proportions in all natural clays, and detains the alkali of the salt by combining with it.

* Sir H. Davy first gave the just explanation of this decomposition. Common salt is a compound of sodium and chlorine. The sodium may be conceived to combine with the oxygen of the water in the earth, and with the earth itself, to form a vitreous compound; and the chlorine to unite with the hydrogen of the water, forming muriatic acid gas. "It is also easy," adds he, "according to these new ideas, to explain the decomposition of salt by moistened litharge, the theory of which has SO much perplexed the most acute chemists. It may be conceived to be an instance of compound affinity; the chlorine is attracted by the lead, and the sodium combines with the oxygen of the litharge, and with water, to form hydrate of soda, which gradually attracts carbonic acid from the air. When common salt is decomposed by oil of vitriol, it was usual to explain the phenomenon by saying, that the acid by its superior affinity, aided by heat, expelled the gas, and united to the soda. But as neither muriatic acid nor soda exists in common salt, we must now modify the explanation, by saying that the water of the oil of vitriol is first decomposed, its oxygen unites to the sodium to form soda, which is seized on by the sulphuric acid, while the chlorine combines with the hydrogen of the water, and exhales in the form of muriatic acid gas."

As 100 parts of dry sea salt, are capable of yielding 62 parts by weight of muriatic acid gas, these ought to afford by economical management nearly 221 parts of liquid acid, specific gravity 1.142, as prescribed by the London College, or 200 parts of acid sp. gr. 1.160, as directed by the Edinburgh and Dublin Pharmacopeias. The fluid ounce of the London College of a wine pint, is equal in weight to 1.265817 lbs. Troy, divided by 16,

being

which gives 453.7 grains Troy. This weight multiplied by 1.142 = the specific gravity of their standard acid, gives the product 520.4; which being multiplied by 0.2763, the muriatic gas in 1.00 by Dr. Ure's table, we have 143.8 or 144 for the acid gas in the liquid ounce, of the above density. We find this quantity equivalent to 200 gr. of carbonate of lime. Had the fundamental number 28.3 of Dr. Ure's table been made 28.6, as one of his experiments related in the Annals of Philosophy indicates, then a liquid ounce of the above acid would have dissolved upwards of 202 grains of pure calcareous carbonate. But when the results fluctuate between 28.3 and 28.6, they become exceedingly difficult to decide upon. As the difference is altogether unimportant in practice, he does not feel himself justified in making any alteration in his table. The limit of its error is certainly a fraction of one per cent. Were 29.0 the leading number, then a liquid oz. of acid of 1.142, would dissolve 205 grains of calc spar. It is obvious that the series of specific gravities given in the above table, is altogether independent of this question. If 28.6 should be preferred by any person, let him multiply this number by 0.9, 0.8, 0.7, 0.6, &c. and he will have a series of numbers representing the quantities of dry acids corresponding to the specific gravities 1.190, 1.1735, 1550, 1.1351, &c. for these densities are opposite to 90, 80, 70, 60, &c. per cent of the strong acid. When this acid is contaminated with sulphuric acid, it affords precipitates with muriates of barytes and strontites.*

We have described the ancient method of extracting the gas from salt, which is now laid aside.

The English manufacturers use iron stills for this distillation, with earthen heads: the philosophical chemist, in making the acid of commerce, will doubtless prefer glass. Five parts, by weight, of strong sulphuric acid are to be added to six of decrepitated sea salt, in a retort, the upper part of which is furnished with a tube or neck, through which the acid is to be poured upon the salt. The aperture of this tube must be closed with a ground stopper immediately after the pouring. The sulphuric acid immediately combines with the alkali, and expels the muriatic acid in the form of a peculiar air, which is rapidly absorbed by water. As this combination and disengagement take place without the application of heat, and the aërial fluid escapes very rapidly, it is necessary to arrange and lute the vessels together before the sulphuric acid is added, and not to make any fire in the furnace until the disengagement begins to slacken; at which time it must be very gradually raised. Before the monearly one and a half the volume of the water. 481 parts occupy only 1.42 in bulk, a condensation of about 340 into one. The consequence of this approximation of the particles, is the evolution of their latent heat; and accordingly the heat produced in the condensation of the gas is so great that it melts ice almost as rapidly as the steam of boiling water does. Hence also in passing the gas from the beak of a retort into a Woulfe's apparatus containing water to be impregnated, it is necessary to surround the bottles with cold water or ice, if we wish a considerable condensation.

Dr. Thomson, in the second volume of his System of Chemistry, 5th edition, has committed some curious mistakes in treating of the aqueous combination of muriatic acid gas. He says, "A cubic inch of water at the temperature of 60°, barometer 29.4, absorbs 515 cubic inches of muriatic acid gas, which is equivalent to 308 grains nearly. Hence water thus impregnated contains 0.548, or more than half of its weight of muriatic acid, in the same state of purity, as when gaseous. I caused a current of gas to pass through water, till it refused to absorb any more. The specific gravity of the acid thus obtained was 1.203. If we suppose that the water in this experiment absorbed as much gas as in the last, it will follow from it that 6 parts of water, being saturated with this gas, expanded so as to occupy very nearly the bulk of 11 parts; but in all my trials the expansion was only to 9 parts. This would indicate a specific gravity of 1.477; yet upon actually trying water thus saturated, its specific gravity was only 1.203. Is this difference owing to the gas that escapes during the taking of the specific gravity?" page 232.

We are here presented with a puzzle for the chemical student; and an instructive example, when one takes the trouble of unravelling the hank, of a contest between experimental results and false computation. Granting all the experimental statements to be exact, none of the consequences follow. For, in the first place, 515 cubic inches of muriatic acid gas do not weigh 308 grains nearly, but only 201 grains; and hence, secondly, his liquid acid could contain at utmost only 0.443 of its weight of gas, instead of 0.548; and, in the third place, the calculated enlargement of bulk is 1.5, or from 6 to 9, and not to 11; so that the quere with which he concludes is superseded. But another quere may here be started, about the experimental results themselves. Dr. Thomson says, that a cubic inch of water absorbs 515 cubic inches of gas, and acquires the specific gravity by experiment of 1.203. Sir H. Davy states, that a cubic inch of water absorbs about 480 cubic

inches of gas, and forms a liquid of specific gravity 1.2109. Now it is remarkable that Dr. Thomson's additional condensation of 35 inches of gas gives a less specific gravity than we have in the stronger acid of Sir H. Davy.

But farther, the table constructed by Sir H. and E. Davy presents for its fundamental density the number 1.20 of Dr. Thomson. Now this particular acid of 1.20 was carefully analyzed by nitrate of silver, and is stated by Sir H. to contain in 100 grains 40.8 grains of condensed gas. Of course we have a remainder of 59.2 grains of water. 40.8 gr. of gas have a volume at the ordinary pressure and temperature of 104 cubic inches, reckoning the weight of 100 cubic inches to be 39.162 gr. with Dr. Thomson. And as 59.2 gr. of water have absorbed 104 cubic inches, we have the following proportion, 59.2: 104:: 252.5: 443. Thus a cubic inch has condensed only 443 cubic inches, instead of 515. as by Dr. Thomson. And whatever error may be supposed to be in their table, it is but minute, and undoubtedly does not consist in underrating the quantity of condensed gas.

By uniting the base of this gas with silver, and also with potassium, Berzelius has lately determined the prime equivalent of muriatic acid to be 3.4261, whence chlorine comes out 4.4261, and muriatic gas 4.4261 + 0.125 (the prime of hydrogen) = 4.5511. But if we take 1.278 as the specific gravity of this acid gas, then the specific gravity of chlorine will be twice that number, minus the specific gravity of hydrogen, or (1.278 × 2) -0.0694 = 2.4866; and as chlorine and hydrogen unite volume to volume, then the relation of the prime of chlorine will

be to that of hydrogen =

2.4866 0.0694

= 35.83.

If we divide this by 8, we shall have 4.48, to represent the prime equivalent of chlorine, and 4.48+0.125 = 4.605 for that of muriatic acid gas.

But if we call the specific gravity of dry muriatic acid gas 1.2590, as Sir H. Davy says it should be by calculation, then the sp. gravity of chlorine becomes 2.4486, and its prime 4.42, a number agreeing nearly with the latest researches of Berzelius.

Muriatic acid, from its composition, has been termed by M. Gay-Lussac the hydrochloric acid; a name objected to, on good grounds, by Sir H. Davy. It was prepared by the older chemists in a very rude manner, and was called by them spirit of salt.*

In the ancient method, common salt was previously decrepitated, then ground with dried clay, and kneaded or wrought

with water to a moderately stiff consistence, after which it was divided into balls of the size of a pigeon's egg: these balls, being previously well dried, were put into a retort, so as to fill the vessel two-thirds full; distillation being then proceeded upon, the muriatic acid came over when the heat was raised to ignition. In this process eight or ten parts of clay to one of salt are to be used. The retort must be of stone-ware well coated, and the furnace must be of that kind called reverberatory.

It was formerly thought, that the salt was merely divided in this operation by the clay, and on this account more readily gave out its acid; but there can be little doubt, that the effect is produced by the siliceous earth, which abounds in large proportions in all natural clays, and detains the alkali of the salt by combining with it.

* Sir H. Davy first gave the just explanation of this decomposition. Common salt is a compound of sodium and chlorine. The sodium may be conceived to combine with the oxygen of the water in the earth, and with the earth itself, to form a vitreous compound; and the chlorine to unite with the hydrogen of the water, forming muriatic acid gas. "It is also easy," adds he, " according to these new ideas, to explain the decomposition on of salt by moistened litharge, the theory of which has so much perplexed the most acute chemists. It may be conceived to be an instance of compound affinity; the chlorine is attracted by the lead, and the sodium combines with the oxygen of the litharge, and with water, to form hydrate of soda, which gradually attracts carbonic acid from the air. When common salt is decomposed by oil of vitriol, it was usual to explain the phenomenon by saying, that the acid by its superior affinity, aided by heat, expelled the gas, and united to the soda. But as neither muriatic acid nor soda exists in common salt, we must now modify the explanation, by saying that the water of the oil of vitriol is first decomposed, its oxygen unites to the sodium to form soda, which is seized on by the sulphuric acid, while the chlorine combines with the hydrogen of the water, and exhales in the form of muriatic acid gas."

As 100 parts of dry sea salt, are capable of yielding 62 parts by weight of muriatic acid gas, these ought to afford by economical management nearly 221 parts of liquid acid, specific gravity 1.142, as prescribed by the London College, or 200 parts of acid sp. gr. 1.160, as directed by the Edinburgh and Dublin Pharmacopeias.

The fluid ounce of the London College being of a wine pint, is equal in weight to 1.265817 lbs. Troy, divided by 16,

which gives 453.7 grains Troy. This weight multiplied by 1.142 = the specific gravity of their standard acid, gives the product 520.4; which being multiplied by 0.2763, the muriatic gas in 1.00 by Dr. Ure's table, we have 143.8 or 144 for the acid gas in the liquid ounce, of the above density. We find this quantity equivalent to 200 gr. of carbonate of lime. Had the fundamental number 28.3 of Dr. Ure's table been made 28.6, as one of his experiments related in the Annals of Philosophy indicates, then a liquid ounce of the above acid would have dissolved upwards of 202 grains of pure calcareous carbonate. But when the results fluctuate between 28.3 and 28.6, they become exceedingly difficult to decide upon. As the difference is altogether unimportant in practice, he does not feel himself justified in making any alteration in his table. The limit of its error is certainly a fraction of one per cent. Were 29.0 the leading number, then a liquid oz. of acid of 1.142, would dissolve 205 grains of calc spar. It is obvious that the series of specific gravities given in the above table, is altogether independent of this question. If 28.6 should be preferred by any person, let him multiply this number by 0.9, 0.8, 0.7, 0.6, &c. and he will have a series of numbers representing the quantities of dry acids corresponding to the specific gravities 1.190, 1.1735, 1.1550, 1.1351, &c. for these densities are opposite to 90, 80, 70, 60, &c. per cent of the strong acid. When this acid is contaminated with sulphuric acid, it affords precipitates with muriates of barytes and strontites.*

We have described the ancient method of extracting the gas from salt, which is now laid aside.

The English manufacturers use iron stills for this distillation, with earthen heads: the philosophical chemist, in making the acid of commerce, will doubtless prefer glass. Five parts, by weight, of strong sulphuric acid are to be added to six of decrepitated sea salt, in a retort, the upper part of which is furnished with a tube or neck, through which the acid is to be poured upon the salt. The aperture of this tube must be closed with a ground stopper immediately after the pouring. The sulphuric acid immediately combines with the alkali, and expels the muriatic acid in the form of a peculiar air, which is rapidly absorbed by water. As this combination and disengagement take place without the application of heat, and the aërial fluid escapes very rapidly, it is necessary to arrange and lute the vessels together before the sulphuric acid is added, and not to make any fire in the furnace until the disengagement begins to slacken; at which time it must be very gradually raised. Before the mo