Part 17

This is an improved and extended table of the force of vapour, similar to that at page 14, vol. I. It shews that the different vapours increase inforce in geometrical progression, to certain intervals of temperature, the same to most or all liquids. These intervals of temperature were presumed in the former table, to be in reality _equal_ to one another; but the accuracy of this last notion has been questioned.

TABLE, _Shewing the expansion of air, and the elastic force of aqueous and ethereal vapour, at different temperatures._ ----------+---------+---------------+----------------+------------- | | Utmost force of | Temperat. | Vol. +---------------+----------------+Weight of 100 | of air. |Aqueous vapour.|Ethereal vapour.| cubic inches ----------+---------+---------------+----------------+ of aqueous -28° | 420 | | | vapour. -20 | 428 |Inches of Merc.|Inches of Merc. | -10 | 438 +---------------+----------------+------------- 0 | 448 | .08 | | Grains. 10 | 458 | .12 | | 20 | 468 | .17 | | 30 | 478 | .24 | | ----------+---------+---------------+ | 32° | 480 | .26 | 7.00 | .178 33 | 481 | .27 | 7.18 | .184 34 | 482 | .28 | 7.36 | .191 35 | 483 | .29 | 7.54 | .197 36 | 484 | .30 | 7.73 | .203 37 | 485 | .31 | 7.92 | .209 38 | 486 | .32 | 8.11 | .216 39 | 487 | .33 | 8.30 | .222 40 | 488 | .34 | 8.50 | .229 41 | 489 | .35 | 8.70 | .235 42 | 490 | .37 | 8.90 | .245 43 | 491 | .38 | 9.10 | .255 44 | 492 | .40 | 9.31 | .267 45 | 493 | .41 | 9.52 | .275 46 | 494 | .43 | 9.74 | .284 47 | 495 | .44 | 9.96 | .293 48 | 496 | .46 | 10.18 | .303 49 | 497 | .47 | 10.41 | .313 50 | 498 | .49 | 10.64 | .323 51 | 499 | .50 | 10.87 | .329 52 | 500 | .52 | 11.10 | .341 53 | 501 | .54 | 11.34 | .354 54 | 502 | .56 | 11.59 | .366 55 | 503 | .58 | 11.85 | .378 56 | 504 | .59 | 12.12 | .384 57 | 505 | .61 | 12.39 | .396 58 | 506 | .62 | 12.66 | .402 59 | 507 | .64 | 12.94 | .414 60 | 508 | .65 | 13.22 | .420 61 | 509 | .67 | 13.51 | .432 62 | 510 | .69 | 13.80 | .444 63 | 511 | .71 | 14.10 | .456 64 | 512 | .73 | 14.41 | .468 65 | 513 | .75 | 14.72 | .480 66 | 514 | .77 | 15.04 | .492 67 | 515 | .80 | 15.36 | .509 68 | 516 | .82 | 15.68 | .521 69 | 517 | .85 | 15.90 | .539 70 | 518 | .87 | 16.23 | .551 71 | 519 | .90 | 16.56 | .569 72 | 520 | .92 | 17.00 | .580 73 | 521 | .95 | 17.35 | .598 74 | 522 | .97 | 17.71 | .610 75 | 523 | 1.00 | 18.08 | .627 76 | 524 | 1.03 | 18.45 | .645 77 | 525 | 1.06 | 18.83 | .662 78 | 526 | 1.09 | 19.21 | .680 79 | 527 | 1.12 | 19.60 | .700 80 | 528 | 1.16 | 20.00 | .721 ----------+---------+---------------+----------------+-------------

_Applications of the above Table._

These tables will be found of great use in reducing volumes of air from one temperature or pressure to any other given one: also in determining the specific gravities of dry gases from experiments on those saturated with or containing given quantities of aqueous or other vapours.

As several writers, and some of considerable eminence, have given erroneous or imperfect formulæ on these subjects, more particularly with regard to the effect of aqueous vapour in modifying the weights and volumes of gases, it has been thought proper to subjoin the following precepts and examples for the use of those who are not sufficiently conversant in such calculations.

The 5th column of the above table, or weight of aqueous vapour, is new, and may therefore require explanation. Gay Lussac is considered the best authority in regard to the specific gravity of steam; but it would be well if his results were confirmed or corrected, as they are of importance. According to his experience, the specific gravities of common air and of pure aqueous vapour, _of the same temperature and pressure_, are as 8 to 5, or as 1 to .625. Now I assume that 100 cubic inches of common air, free from moisture, of the temperature 60° and the pressure of 30 inches of mercury, weigh 31 grains nearly. It is an extraordinary fact that philosophers are not agreed upon the absolute weight of a given volume of common air. Most authors now assume the weight of 100 inches = 30.5 grains, whilst according to my experience it is more than 31 grains. If common air be assumed 31 grains, steam would be 19⅜ grains for 100 cubic inches, at the same temperature and pressure, could it subsist; but as it cannot sustain that pressure at the temperature of 60° we must deduct according to the diminished pressure, the utmost force of steam at 60° being .65 parts of an inch of mercury, we have 30 inches ∶ 19⅜ grains ∷ .65 ∶ .420 grains = the weight of 100 cubic inches of aqueous vapour at 60° and pressure .65 parts of an inch; which is the number given above in the table. The like calculation is required for any other pressure: but in addition to this, there is to be an allowance for the temperature from the 2d column: Thus, let the weight of 100 cubic inches of steam at 32° be required. We have 30 inch. ∶ 19⅜ grs. ∷ .26 inch. ∶ .1679 grs.; the weight of 100 inches of steam at 60°; then if 480 ∶ 508 ∷ .1679 ∶ .178 grs. = weight of 100 cubic inches of steam at 32° and pressure .26 parts of an inch, the tabular number required.

_Examples._

1. How many cubic inches of air at 60° are equivalent in weight to 100 cubic inches at 45°?

By the column headed _volume of air_ we have this proportion, if 493 ∶ 508 ∷ 100 inch. ∶ 103.04 inches, the volume required.

2. How many cubic inches of air with the barometer at 30 inches height, are equal in weight to 100 cubic inches when the barometer stands at 28.9 inches?

_Rule._ The volume of air being inversely as the pressure, we have, 30 ∶ 28.9 ∷ 100 inches ∶ 96⅓ inches the answer.

3. How many cubic inches of dry air are there in 100 inches saturated with aqueous vapour, at the temperature of 50°, and pressure 30 inches of mercury?

Here the formula

(_p_ - _f_) ----------- _p_

applies, where _p_ denotes the atmospheric pressure at the time, and _f_ denotes the utmost force of vapour in contact with water at the temperature. Hence _p_ = 30, _f_ = .49 per table, and we have

(_p_ - _f_) (30 - .49) 29.51 ----------- = ----------- = ----- = 98¹¹/₃₀, or _p_ 30 30

98¹¹/₃₀ percent dry air. & 1¹⁹/₃₀ vapour. --------- 100.

If the vapour of ether is assumed, then _f_ = 10.64, and we have

(_p_ - _f_) (30 - 10.64) 19.36 ----------- = ----------- = ----- = _p_ 30 30

.645, ... or 64½ per cent dry air.[28] 35½ per cent ethereal vapour. ----- 100

[Footnote 28: The aqueous vapour in this case maybe considered as insignificant.]

4. Suppose we find by trial the weight of 100 cubic inches of common air saturated with vapour at 60°, the barometer standing at 30 inches to be 30.5 grains, and the weight of hydrogen gas in like circumstances to be 2.118 grains; query the weights of 100 cubic inches of each gas free from vapour, and their specific gravities, the temperature and pressure being as above?

If 30.5 ∶ 2.118 ∷ 1 ∶ .0694 = sp. gr. of vapourized hydrogen, that of vapourized air being 1. Subtracting .42 grs. (weight of vapour per table) from 30.5 grs., leaves 30.08 grains; and subtracting .65 parts of an inch from 30 inches, leaves 29.35 inches. Hence 100 cubic inches of dry air at the pressure of 29.35 inches, weigh 30.08 grains; and we have 29.35 ∶ 30 ∷ 30.08 ∶ 30.746 grains, the weight of 100 inches of dry air. Again, subtracting .42 grs. from 2.118, leaves 1.698 grains = weight of 100 cubic inches of hydrogen of 60° and sustaining the pressure of 29.35 inches; whence if 29.35 ∶ 30 ∷ 1.698 ∶ 1.736 grains, weight of 100 inches of dry hydrogen; and 30.746 ∶ 1.736 ∷ 1 ∶ .05645 = sp. gr. of dry hydrogen, that of dry air being unity. Or the results may be exhibited as under:

Weight of 100 cubic inches. Sp. Gravities.

Vap. air 30.5 grains 1 14.4 Vap. hydrogen 2.118 ---- .0694 1

Dry air 30.746 grains 1 17.7 Dry hydrogen 1.736 ---- .05645 1

FORMULÆ FOR DETERMINING THE PROPORTIONS OF COMBUSTIBLE GASES IN MIXTURES.

It frequently happens, especially in the decomposition of vegetable substances by heat, that the product consists of several combustible gases in mixture, and it is desirable to determine the proportions of each of those which collectively constitute the mixture. The following forms will be found useful for this purpose.

1. _Carbonic oxide and hydrogen._

Let _x_ = the volume of carbonic oxide, _y_ = that of hydrogen, _w_ = that of mixture, and _a_ = that of carbonic acid, produced by exploding the mixed gases with oxygen over mercury.

Then the carbonic oxide, or _x_ = _a_, and the hydrogen, or _y_ = _w_ - _a_.

2. _Sulphuretted hydrogen and hydrogen._

Let _x_ = the volume of sulphuretted hydrogen, _y_ = that of hydrogen, _w_ = that of the mixture, and _g_ = the oxygen spent in the combustion of _w_.

Then because _x_ + _y_ = _w_, and 1½_x_ + ½_y_ = _g_; we have _x_ = _g_ - ½_w_, and _y_ = 1½_w_ - _g_.

3. _Phosphuretted hydrogen and hydrogen; also carburetted hydrogen and hydrogen, and carburetted hydrogen and carbonic oxide._

The notation being as above, we have _x_ + _y_ = _w_, and 2_x_ + ½_y_ = _g_ (see page 171): and,

2_g_ - _w_ 4_w_ - 2_g_ _x_ = -----------, and _y_ = -----------. 3 3

4. _Olefiant gas and carburetted hydrogen._

The notation being as above, we have

_x_ + _y_ = _w_, and 3_x_ + 2_y_ = _g_; whence _x_ = _g_ - 2_w_ and _y_ = 3_w_ - _g_.

5. _Carburetted hydrogen, carbonic oxide and hydrogen._

Let _x_ = carburetted hydrogen, _y_ = carbonic oxide, _z_ = the hydrogen, _g_ = the oxygen spent in the combustion of _w_ volumes of mixed gas, and _a_ = the carbonic acid produced.

Then _x_ + _y_ + _z_ = _w_, _x_ + ½_y_ + ½_z_ = _g_, and 2_x_ + _y_ = _a_.

whence we have

2_g_ - _w_ 3_a_ - 2_g_ + _w_ _x_ = -----------, _y_ = ----------------- 3 3

and _z_ = _w_ - _a_.

6. _Olefiant gas, carburetted hydrogen and carbonic oxide._

Let _a_ = the olefiant gas, _y_ = the carburetted hydrogen, and _z_ = equal the carbonic oxide, _g_ = the oxygen entering into combination, and _a_ = the carbonic acid produced; also _w_ = the whole volume as before.

Then we have _x_ + _y_ + _z_ = _w_, 3_x_ + 2_y_ + ½_z_ = _g_, and 2_x_ + _y_ + _z_ = _a_.

Whence _x_ = _a_ - _w_,

_y_ = 4_w_ - 5_a_ + 2_g_ -------------------, 3

and _z_ = ⅔(_w_ + _a_ - _g_).

7. _Superolefiant gas,[29] carburetted hydrogen, and carbonic oxide._

[Footnote 29: A gas found in oil and coal gas. See Manchester Memoirs, vol. 4 (new series), page 73.]

Let _x_ = volume of superolefiant, _y_ = volume of carburetted hydrogen, _z_ = volume of carbonic oxide, _g_ = the oxygen combining, _a_ = carbonic acid produced, and _w_ = volume of mixed gas.

Then _x_ + _y_ + _z_ = _w_, 4½_x_ + 2_y_ + ½_z_ = _g_, and 3_x_ + _y_ + _z_ = _a_.

Whence _x_ = _a_ - _w_ ----------, 2

_y_ = 3_w_ - 4_a_ + 2_g_ ------------------, 3

and _z_ = 3_w_ - 4_g_ + 5_a_ -------------------. 6

8. _Superolefiant gas, carburetted hydrogen, carbonic oxide, and hydrogen._

This is the mixture of gases obtained by a red heat from coal and oil, after being freed from carbonic acid, &c., by the usual means.

This mixture requires a very complicated formula, in consequence of the specific gravities of the gases entering into the calculus. The importance of the subject however may be an apology for the labour.

Let _x_ = vol. of superolefiant, _S_ its sp. gr. _y_ = vol. of carb. hydrogen, ∫ its sp. gr. _z_ = vol. of carbonic oxide, _c_ its sp. gr. & _u_ = vol. of hydrogen, _s_ its sp. gr.

_C_ = specific gravity of the mixture, _g_ = oxygen, _a_ = carbonic acid, and _w_ = whole volume of mixture as before.

Then we have _x_ + _y_ + _z_ + _u_ = _w_ 4½_x_ + 2_y_ + ½_z_ + ½_u_ = _g_ 3_x_ + _y_ + _z_ = _a_ and _Sx_ + ∫_y_ + _cz_ + _su_ = _Cw_.

Whence _u_ =

(3_S_ + 5_c_ - 8∫)_a_ - (4_c_ - 4∫)_g_ - (3_S_ + 6_C_ - 6∫ - 3_c_)_w_ -------------------------------------------------------------------- 8∫ + _c_ - 3_S_ - 6_s_.

The value of the hydrogen being obtained, it may be subtracted from _w_, and the remainder will be best divided into three portions, by the preceding formula.

HEAT PRODUCED BY THE COMBUSTION OF GASES.

Subsequent experience to that detailed at page 77, Vol. 1. has furnished the following more correct results of the heat produced by the combustion of pure gases.

Hydrogen, combustion of it raises an equal volume of water 5° Carbonic Oxide 4½ Carburetted Hydrogen, or Pond Gas 18 Olefiant Gas 27 Coal Gas (varies with the gas from 10° to) 16 Oil Gas (varies also with the gas from 12° to) 20

Generally the combustible gases give out heat nearly in proportion to the oxygen they consume. See note at the end of Vol. 4, new series of the Manchester memoirs.

ABSORPTION OF GASES BY WATER, &c.

This curious subject has attracted much less attention than it deserves. Very little has been published relating to it since the time of Dr. Henry’s essays and my own, now more than twenty years ago. The only author I remember is M. Saussure of Geneva, who published a similar essay about twelve years afterwards. See Thomson’s Annals of Philosophy, Vol. 6. He investigates the quantities of gases absorbed by various solid bodies, in a manner which I do not fully comprehend; he then treats of the absorption of gases by liquids, adverting at the same time to Dr. Henry’s experiments and mine. My enquiries were principally confined to _one_ liquid, water; but I made a few trials with others, such as weak aqueous solutions of salts, alcohol, &c., and observing no remarkable differences, I concluded somewhat too hastily that “most liquids free from viscidity, such as acids, alcohol, &c., absorb the same quantity of gases as pure water.” Manchester memoirs, new series, Vol. 1. M. Saussure however asserts that there are considerable differences in liquids in this respect. He finds sulphuretted hydrogen to be more absorbable by water than Dr. Henry and I did; in this I find he is right. Water takes about 2½ its bulk of this gas when pure; and it seldom had been obtained unmixed with hydrogen when Dr. Henry and I made our experiments upon its absorption. In regard to carbonic acid, nitrous oxide, and olefiant gas, M. Saussure nearly agrees with us; but his results with oxygen gas, carbonic oxide, carburetted hydrogen, hydrogen and azote, would prove that water absorbs twice the quantities of each that we have assigned. I have no doubt he is wrong in the less absorbable gases. In the case of absorption of mixed gases, Saussure has given four examples, in which he finds the results to militate against my theoretic view, as stated at page 201, Vol. 1.; namely, that water takes the same quantity of each in a mixed state as it would do if they were separate, and in other respects in like circumstances. But I have shewn in the Annals of Philos. Vol. 7, 1816, that his results coincide as near as any one can expect with the views which I have all along taken of this subject.

It will be seen, page 173, that another gas has been found to coincide with olefiant gas in absorbability; namely, phosphuretted hydrogen.

FLUORIC ACID.--DEUTOXIDE OF HYDROGEN.

In treating of Fluoric acid, (Vol. 1, page 277) we came to the conclusion that this acid was probably constituted of two atoms of oxygen, and one of hydrogen, and have figured it accordingly (Plate 5, fig. 38). Subsequent experience however has shewn that deutoxide of hydrogen, though it can be formed synthetically, is not the same thing as fluoric acid. We are indebted to M. Thenard for the discovery of this curious compound, the deutoxide of hydrogen or oxygenated water. An ingenious memoir on the subject was published by him in 1818, in which the formation and the properties of this compound are fully detailed. I had no small satisfaction in 1822, when at Paris, in being obligingly favoured by M. Thenard with a view of the process of the formation, and of the more distinguishing properties of this singular liquid.

The nature of fluoric acid is still enveloped in obscurity. My experience led me to adopt the composition of fluate of lime to be 40 acid and 60 lime per cent. I had not then seen Scheele’s admirable essay on the subject. From the 5th section of his 2d. essay on fluor mineral, 1771, it may be deduced that fluate of lime is composed of 72.5 lime and 27.5 acid per cent. In 1809 Klaproth, and near the same time, Dr. Thomson found about 67½ lime and 32½ acid per cent. in fluor spar. They both erred, no doubt, as I did, by not repeating the treatment of the mineral with sulphuric acid often enough. Since then most authors, as Davy, Berzelius, Thomson, &c., agree with Scheele nearly, in assigning 27.5 acid, and 72.5 lime, in 100 parts of fluate of lime. My experience in 1820 gave me 1 per cent. less of lime; and Dr. Thomson now finds about 1 per cent. more of lime than Scheele’s analysis gives.

If we estimate the atom of lime at 24, that of fluoric acid must be about 9, according with the above proportion; this is much below 15, the weight of an atom of deutoxide of hydrogen.

Should Sir H. Davy’s view of fluate of lime be found correct, its atomic constitution would be one atom of _calcium_, the metallic substance of which lime is the protoxide, and one atom of _fluorine_, the name he has assigned to the other element, which with hydrogen is supposed to constitute the fluoric acid. The atom of fluor spar would then be 1 atom of calcium, 17, united to one atom of fluorine 16.

MURIATIC ACID.--OXYMURIATIC ACID, &c.

From the articles _muriatic acid_ and _oxymuriatic acid_ in the former volume, published now 16 years ago, as well as from the appendix to said volume, in which sundry animadversions are found on the fluctuating opinions entertained in regard to these acids, the reader will not be surprised to find some further addition.

Three notions have been submitted to the public in the last twenty years in regard to the nature of muriatic acid. First, the gas detached from common salt by sulphuric acid has been thought to be the acid in a state of purity, and constituted of a certain base or radical united to oxygen; this was the notion inculcated in the articles alluded to above. Second,--it is stated as a fact that when oxymuriatic acid and hydrogen in equal volumes are united by the electric spark, a volume of muriatic acid gas is the result equal to the sum of both the other volumes, and that this gas perfectly agrees with the gas obtained from common salt by sulphuric acid; this suggested the idea that muriatic acid gas is a compound of what has been called _real_ or _dry_ muriatic acid one atom, and water one atom. And, third, it is argued, that the element we have called oxymuriatic acid gas, is, for aught that appears, a _simple_ body, and consequently, that muriatic acid gas is the _real acid_, and is constituted as above, of one atom of hydrogen, and one atom of oxymuriatic acid (now called _chlorine_.) It is not intended here to enter into a discussion of the arguments and facts adduced in support of the different conclusions. More experience must be had before all the doubts and difficulties are removed from the subject. But it will be proper to illustrate these different positions by an example. For instance, common salt, muriate of soda or chloride of sodium. By the first notion 50 parts of dry common salt will consist of one atom of muriatic acid gas, 22, and one atom of caustic soda, 28. By the second notion the same salt will be formed of 30 parts of muriatic acid gas, and 28 of caustic soda; but 8 parts of water evaporate when the salt is dried. By the third view common salt consists of oxymuriatic acid, or chlorine and sodium, or the metal of which caustic soda is the protoxide; and 50 parts of salt will consist of 29 chlorine and 21 sodium, or one atom of each.

NITRIC ACID--COMPOUNDS OF AZOTE AND OXYGEN.

Since the account of nitric acid (Vol. 1, page 343) was printed, a change has universally taken place in estimating the weight of the nitric acid atom, and of the proportion of azote and oxygen in the same. This has been effected chiefly by a more correct analysis of nitre than existed at that time. Nitre is now found to consist nearly of 52 parts acid and 48 parts potash per cent. Hence if the atom of potash be 42, that of nitric acid must be 45; for, 48 ∶ 52 ∷ 42 ∶ 45, nearly. That is, the nitric acid atom consists of 10 azote + 35 oxygen by weight; or of 2 atoms of azote (according to my estimate) and 5 of oxygen. There appear to be _two_ nitrous acids; namely, the one which I have designated by that name, which may now be called _subnitrous_, or as Gay Lussac terms it _pernitrous_; and the other what I considered as _nitric acid_ in the former volume, composed of 1 atom azote, and 2 of oxygen.

Real nitric acid then is that combination which is effected by uniting oxygen with a minimum of nitrous gas; or 1 measure of oxygen with 1.3 nitrous gas, (See Vol. 1, page 328). The oxynitric acid, which I was led to infer from the last mentioned combination, (1 azote with 3 oxygen) does not appear to exist. The Table of nitric acid (Vol. 1, page 355) will require some correction. An increase of about 4 per cent. should be made, I apprehend, on the quantities of acid corresponding to the several specific gravities.