oxigen, equal to 37.5 grains, combined with one of potash, equal to 48, must unite in triple union with one of oximuriatic gas equal to 329, to form one proportion, equal to 118.4 grains, of hyperoximuriate of potash.

(To be concluded in our next.)

VI.

Farther. Account of a Mule Animal between the Male Ass and Female Zebra. In a Letter from THOMAS ANDREW KNIGHT, Esq., F. R. S., &c.

Dear Sir,

IN

To W. NICHOLSON, Esq.

N a former number of your Philosophical Journal* you Offspring of an have given an account of a mule animal between the male ass and zebra. ass and female zebra, which was bred by the present Earl of Powis; and you have expressed a wish to obtain farther information respecting it: I in consequence send you the following particulars.

by colour.

You have justly stated, that the zebra would not admit Wild animals the approach of the ass till his coat had been properly distinguish painted to resemble her own; which circumstance is curitheir species ous, because it goes far to prove, that animals, in a state of nature, distinguish and select those of their own species, in part at least, by sight; while in a state of domestication, when their colours become varied by the influence of cultivation, they appear to be guided almost entirely by another sense.

The animal, which I proceed to describe, like other The animal mules, bore, externally, a greater resemblance to its male more resernbled the male than to its female parent; and until by near approach its than the female stripes, which were much less distinct than those of the ze- parent, bra, became visible, it was not readily distinguishable from

Received from the Right Hon. Sir Joseph Banks, Bart., P. R. S.;

and inserted Vol. II, p. 267 of the quarto series.

was intractable,

mule.

Died from an

a very large and strong Spanish ass. I am ignorant whether nature has given to the zebra, as to the ass, the power of breathing through its mouth as well as through its nostrils; or whether the passage of the breath is confined to the nostrils only, as in the horse: but I observed, that the mule zebra uttered its cry, which a good deal resembled the braying of an ass, through its mouth; corresponding in this respect with the male, which is obtained from the male ass and the mare, and differing from that which is derived from the horse and the female ass.

The temper of the mule zebra, as might have been expected from its parentage, was sullen, vindictive, and untractable. It was nevertheless sufficiently subdued to permit itself to be ridden; but a cousiderable time generally elapsed before the mule and. the rider could agree about the direction in which they were to move; and when that. point was in some degree settled, the labour, to the rider, of impelling and guiding his companion, was found so much to exceed that of walking on foot, that the services of the mule were not much in repute, or often called for.

and a complete Attempts were made to obtain offspring from it both by the female ass, and the mare; but neither were successful. It appeared to possess passions; but, like other mules, to be without powers. It met its death by an accident when accident at four rising four years old, and consequently before it had ac quired its full growth and strength: but its size and form, at that age, indicated great powers of bearing weight and undergoing fatigue; and it would probably have been of great value both as a beast of burden and draught, had not its temper disqualified it for either office.

years old.

I am, dear Sir,

Your obedient servant,

THOMAS ANDREW KNIGHT.

Downton, April the 26th, 1811.

VII.

Remarks on Potassium, Sodium, &c.; in Reply to the Communications of JUSTUS. BY JOHN DALTON.

SIR,

To Mr. NICHOLSON,

IN perusing the former of the two communications, pur

muriatic acid.

porting to be a reply to the remarks on potassium and sodium in my New System of Chemical Philosophy, (Journal, vol. 28, p. 67) I felt interested in various acute observations of your correspondent; but at p. 72, where he inves- Quantity of tigates the quantity of oxigen in a given volume of oximu- oxigen in oxiriatic acid gas, I am quite at a loss to conceive how he had obtained so small a portion as 30.24 per cent, when I had found 50, (New System, p. 560) calculating from the best data I could procure, and which I was confident from my own experience could not be materially incorrect. Being at that time particularly engaged, I could not attend to the subject farther than to write a short note (Journal, p. 157) requesting an explanation. This was given in the ensuing number, (p. 219.) When I stated, that his data were de fective, I did not mean erroneous; no mathematician would have understood me in that sense; I meant, that he had not given sufficient data, and consequently that he had made the problem an unlimited one. If I should propose the following question to your correspondent, namely, How long would a body be in moving with a uniform velocity from the Earth to the Moon, or through a space of 240,000 miles— would he not find it necessary, that the velocity should be given? Yet he has found means to answer a similar question without the requisite data. The accuracy of the answer then may well be suspected. It may be of service to your correspondent, and perhaps to others of your readers, if I make out this charge more particularly. According to Chenevix,

77.5 mur. acid + 22′5 oxigen = 100 oximur. acid, by wt. X 22.5 oxi. 118

then, by measure 77.5 mur. acid

measures;

VOL. XXIX.-JUNE, 1811.

1.73 1.126

Potassium

ash and hidrogen.

That is, 775 measures of muriatic acid + 34.5 measures of oxigen, together 112 measures, will, when chemically combined, be equal to a measures of oximuriatic acid gas. How your correspondent ascertains the value of x in the above equa tion to be 100, I know not. It may as easily and as probably be assumed 50 or 500. Surely he is not so ignorant of Mr. Davy's experience as not to know, that 775 measures of muriatic acid gas + 34.5 of oxigen, are far inferior in -weight to 100 measures of oximuriatic acid. The truth is, the specific gravity of oximuriatic acid gas is a datum most obviously necessary in the estimation of the oxigen a given volume of it contains.

With regard to the facts and arguments respecting pocontains pot tassium and sodium, I can bring forward the following, namely, that fused hydrate of potash consists of potash, and water, or potash, hidrogen, and oxigen; that in the decomposition of this article by Voltaic electricity, nothing but oxigen gas is evolved, and potassium remains; hence I conclude, that potassium contains, and probably consists of potash and hidrogen. If your correspondent is not satisfied with these facts, and this reasoning, I cannot convince him. The first fact I adopt from my own experience and that of others, the second from that of Mr. Davy; and I am not able to discover any flaw in the conclusive argument.

Heat separates

ash, and eva. porates them

at a certain de gree, whether chemically

combined is not known,

As to the question, what is the power that produces the water and pot separation of water and potash? I answer, heat. When I say, that, by the application of heat to a certain degree, « the alkali and water both evaporate," no one has authority from me to add "in a state of chemical union," nor yet "in a separate state," though only one of the two ways is likely to be true. The fact was, I had not ascertained when I wrote that, nor indeed have I yet, which of the two is true. I am rather inclined to the latter; but as this is one of a large class of chemical facts, I wish to have more experience, and more time to reflect upon it, than at present I possess. It forms an important inquiry according to my views of chemistry, to ascertain the relation of water to the acids, alkalis, &c. in the very act of distillation; name"ly, whether the water in passing over is in a state of steam, such as we find it in the atmosphere, or in a gasiform state

of

of chemical union with the acid, &c. But, whichever be the case, it is true, "that the process cannot be used to expel the last portion of water from the alkali", when the object is to obtain a ponderable mass of alkali free from

water.

in an open

When fused potash is exposed to a red heat in an open Potash exvessel, white fumes are observed to play over it; these, no posed to heat doubt, are the particles or small drops of the condensed vessel, and in liquid hydrate, similar to the visible mist or condensed a gunbarrel, steam over hot water. From this and the above observation, then, it is probable, that in the gun barrel experiment, not only particles or atoms of hydrate of potash, but also of potash, and of steam, may come into contact with the redhot iron; hence may be explained the production of hydruret of potash or potassium, of oxide of iron, of hidrogen, Alloy of pot and of the white amalgam or alloy of potash and iron. This ash and iron. last is easily exhibited by keeping carbonate of potash in fusion for some time in an iron spoon by an intense heat; after the potash is washed off, the whole surface of the spoon, which has been in contact with the fused carbonate, is white as if tinned, and may be acted upon by an acid without losing its colour*.

As for the complex nature of the decomposition of hy- Complex nadrate of potash, I see no great reason to wonder at it. The ture of the decomposition of article consists of 3 elementary principles; so does wood. hydrate of potWhy, it may with equal propriety be asked, does wood, in ash. its decomposition by heat, exhibit such a mixture of principles? Charcoal, water, carbonic acid, carbonic oxide, carburetted hidrogen, and hidrogen, are among the products of the destructive distillation of wood.

I was surprised at your correspondent's observations on Levity of pothe argument I have drawn for potassium being a compound tassium.

of hidrogen from its levity. I venture to say, that Mr. Davy will allow the argument to have some force. In the place referred to, Mr. Davy does not say a word about the notion, that hidrogen united to potash ought to make a compound specifically lighter than potash. His answer, which is pertinent and to the purpose, is to those who object to potassium and sodium being classed amongst the metals,

* On potassated iron see also Journal, Vol. XXV, p. 51.