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acid, will be nothing more than a solution of pure acetic acid (vinegar) in pure water.

Before tracing the application of sulphurous acid gas to the sugar refining process, it will be necessary to examine the effect of the acetates of lead generally (there are more than one; we have been dealing with the mono or neutral acetate) on certain organic solutions. For this purpose we will take a solution of muscovado or common yellow sugar, about the strength of one of sugar to six of water (both by weight). Solution having been effected by means of heat and agitation, add to it portions of solution of acetate of lead, or, still better, the tris-acetate, commonly known in druggists' shops as Goulard's extract, until most of the colouring matter has become deposited. I say most, because the latter portions of colouring matter cling to the sugar solution with great obstinacy, and cannot be gotten rid of without the expenditure of more acetate of lead than is from motives of economy desirable. You will observe that on now filtering the sugar solution thus treated, the filtrate will be almost devoid of colour, hence the acetate, or rather the tris-acetate of lead would be the very best substance, could it be safely used, to be employed for the purification of yellow sugar. It is quite evident, however, that the employment of this material must remain out of the question until the discovery of some inexpensive, readily-applied and unfailing plan of extracting superabundant lead has been devised. All the ordinary precipitants for lead had been tried without avail, until Dr. Scoffern bethought himself of sulphurous acid, which answers completely. The process has now been in extensive operation for more than six years, and no untoward accident has occurred from the use of the poisonous agent.

This is a convenient opportunity for the introduction of some remarks on chemical nomenclature, having special reference to the compounds of oxide of lead with acetic acid, and of very general application in other cases. You will remember that I denominated the Goulard's extract employed in our sugar refining experiment by the name of tris-acetate or sub-acetate of lead; let us therefore investigate the meaning of those terms. Tris is evidently a prefix signifying three of something; sub is a prefix which means an under or diminished quantity of something. We will proceed to investigate the exact meaning of these terms. Beginning with sugar of lead, this is the neutral acetate; it is composed of one equivalent of These conditions being complied with, copious volumes of base (oxide of lead) combined with one equivalent of acetic two gases, sulphurous acid and carbonic acid, are evolved; acid. Now the chemico-algebraical notation or symbol for permeate the liquor and throw down sulphate of lead. As to lead is Pb (contraction for "Plumbum," and the symbol for the carbonic acid it does no harm, for so long as sulphurous oxygen is O, consequently oxide of lead (protoxide) being acid passes, no carbonate of lead' is found. By proceeding composed of one equivalent of lead plus one of oxygen, its thus, the operator will discover that every trace of lead is symbol is Pb O. removed from the solution, which, if exposed for some days to a warm atmosphere, in order to get rid of lingering sulphurous

VOL. V.

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of lead. But it so

THE POPULAR EDUCATOR.

happens that there are other acetates of

PbO).

fore PbOA or PbO, A represents neutral or mono-acetate
Again, A is the contracted symbol for acetic acid; there-
lead, in number somewhat doubtful, perhaps five or six, all of
which contain an excess of base (oxide of lead, or
Indefinitely therefore they may be generalized as sub-acetates
of lead; but if we desire to be precise, and indicate what kind
of sub-acetate of lead any particular one may be, we must have
recourse to numeral prefixes, and chemists have long agreed
to indicate all excess of base in any salt by prefixes of Greek
origin. Thus mono-acetate of lead remains neutral acetate;
di-acetate, the particular subsalt generated by combination of
two of base with one of acid; tris-acetate, the particular sub-
salt generated by combination of three of base with one of acid,
and so on for the rest. Furthermore, it should be remarked,
that, in addition to the general or indefinite word sub-salt,
there is another very much employed in modern chemical
treatises: I mean basic salt; that is to say, a salt in which the

base predominates.

And this is man:-Oh! ask of him,
The gifted and forgiven,-
While o'er his vision, drear and dim,
The wrecks of time are driven;
If pride or passion in their power,
Can chain the time, or charm the hour,
Or stand in place of heaven?

He bends the brow, he bows the knee,-
"Creator, Father! none but thee!"

ON PHYSICS, OR NATURAL PHILOSOPHY,

No. XXX.
CALORI C.
Continued from page 36.)

THE following table will be found of great utility in convert

of cupellation, or separation of lead from silver, and indeed into the corresponding number of degrees on either of the other In our next lesson we shall enter upon the important processing the number of degrees on any of the three different scales gold by aid of fire. It is an operation of great beauty and of scales, viz. Fahrenheit's, Reaumur's, and the Centigrade.

particular interest just at this time, when so many persons are
devoting their attention to the study of the precious metals.

This table will be extremely useful to Students of Chemistry and Natural Philosophy, especially in reading the accounts of

The operation of cupellation will require the possession of French and other continental discoveries in these sciences. the practice of the art, he will also require several pieces of to make our Students refer to it in future Lessons. Experisome bone ashes. If the student desire to enter very far into We shall have frequent occasion to refer to it ourselves, and the operation, however, admits of being taught by the aid of P.E., were it for the table only, as it will save their making apparatus, to be described in our next. The mere theory of mental Chemists will do well to purchase this number of the a blowpipe operation. The preparation of bone ash is a matter calculations, and prevent their committing mistakes in conof no

let them remain until every thing capable of
away has been removed-in other words, until being burned
quite white. Remove them then from the fire, and when cold
powder them.

MAN.

(From the New York Evening Post.)
THE human mind, that lofty thing!
The palace and the throne,
Where reason sits a sceptred king,

And breathes his judgment tone,
Oh! who with silent step shall trace
The borders of that haunted place,
Nor in his weakness own
That mystery and marvel bind
That lofty thing,-the human mind!
The human heart,-that restless thing!
The tempter and the tried;
The joyous, yet the suffering,-

The source of pain and pride;
The gorgeous thronged,-the desolate,
The seat of love, the lair of hate,-
Self-stung, self-deified!

Yet do we bless thee as thou art,
Thou restless thing,-the human heart!
The human soul,-that startling thing!
Mysterious and sublime!
The angel sleeping on the wing

Worn by the scoffs of time,

The beautiful, the veiled, the bound,
The earth-enslaved, the glory-crowned,
The stricken in its prime!
From heaven in tears to earth it stole,
That startling thing,-the human soul!

another.

divided into three columns, headed Degrees of Fahrtively, In explanation of the following table, we observe that it is Degrees of the Centigrade, and Degrees of Reaumur, respectively. The table commences with the number of the degrees marked at the boiling point on each scale, and gradually decreases by 1 degree, and in some cases by parts of a degree, to -42°-25 Fahrenheit, -41.25 Centigrade, and -33° Reaumur. Thus, suppose that when the temperature of a body is 2009 Fahrenheit, and you wish to know what it is on the Centigrade scale, and on Reaumur's; by turning to the number 200 in the column headed Degrees of Fahrenheit, you find in the hori zontal line with 200, and in the other two columns to the right, the numbers 93.33 and 74-66, which indicate that the corresponding degrees of the given temperature are 98-33 on the Centigrade scale, and 74° 66 on Reaumur's.

• The composition of acetic acid is 4 equivalents of carbon + 3 of hydrogen + 3 of oxygen; hence its full symbolic notation is C4 H3 03; but this being somewhat inconvenient, chemists usually represent it by its initial letter A with a dash over it, thus A; and here it may be remarked that a dash over a letter signifies the body to be of the organic kingdom, i. e. either of animal or vegetable origin, whereas a dash under an initial is a reduplication of quantity. Thus A means acetic acid, and Ā 2 of acetic acid.

Again suppose that when the temperature of a body is 70° Centigrade, and you wish to know what it is on Fahrenheit's and Reaumur's scale; by turning to the number 70 in the column headed Degrees of the Centigrade, you find in the hori zontal line with 70, and in the other two columns, one to the left and one to the right, the numbers 158 and 56, which indicate that the corresponding degrees of the given temperature are 158° on Fahrenheit's scale, and 56° on Reaumur's.

Lastly, suppose that when the temperature of a body is 59° Reaumur, and you wish to know what it is on the Centigrade scale and on Fahrenheit's; by turning to the number 59 in the column headed Degrees of Reaumur, you find in the horizontal line with 59, and in the other two columns to the left, the numbers 73-75 and 164·75, which indicate that the correspond ing degrees of the given temperatures are 739-75 on the Centigrade scale, and 1649-75 on Fahrenheit's.

When the proposed number of degrees on Fahrenheit's ther mometer exceed the limits of the table, that is, are above the boiling point, then the rules given in our last Lesson must be employed, in order to convert them into the corresponding number on the other two scales. Thus, suppose that the temperature of a body, as indicated by Fahrenheit's thermometer, was 600°, and it was required to find the correspond. ing number of degrees on the Centigrade and Reaumur's, we have the following calculations :

32

568

6000

32

568

IL

9)2840-60

315-55 Centigrade.

9)2272:00

25244 Reaumur's:

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52

TABLE OF CONVERSION-continued.

Degrees

of

Degrees of the

Degrees

Degrees

Degrees

Degrees

Degrees

Degrees.

of

of

of the

of

Fahrenheit. Centigrade. Reaumur. Fahrenheit. Centigrade. Reaumur. Fahrenheit. Centigrade. Reaumer. Fahrenheit. Centigrade.] Reaumur.

Degrees

Degrees Degrees

Degrees

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Displacement of the Standard Point.-Thermometers, constructed even with the greatest care, are subject to one cause of error which it is important to observe; it is this: that after a certain time, the standard point, which is zero on the centigrade, and 32o on Fahrenheit's thermometer, tends to rise, so that sometimes it is found out of its place by as much as 2° on the former, and nearly 4° on the latter; that is, the mercury no longer descends to the fixed point of the scale, when the thermometer is immersed in melting ice. Various explanations of this phenomenon have been given, but none appears to be quite satisfactory. It has been attributed to a diminution of the volume of the bulb, arising from the effect of the exterior pressure of the atmosphere, as a vacuum exists in the thermometer; but it has been observed that thermometers which contain air change like those which contain a vacuum. It has been also said that the glass of the bulb, after it has been blown, returns but very slowly to its

primitive state of aggregation, this explanation being founded on the supposition that, at the end of two or three years, the fixed point is no longer subject to displacement. But, according to the experiments of M. Despretz, this displacement appears to continue during a period almost indefinite. Besides this slow displacement, sudden variations in the position of the fixed point have been observed, whenever the thermometer has been raised to a high temperature. Indeed, if at that time we immerse the instrument in melting ice, the mercury sinks no longer to the freezing point on the scale, and it returns to it only at the end of a certain period. It is of importance, therefore, when it is required to measure tem peratures with precision, first to verify the position of the fixed point in the thermometer which is about to be employed. M. Regnault has found also that some mercurial thermome ters which are accurate with respect to the two fixed points on the scale, namely, the freezing and the boiling points, are not so between these points, and that their indications some times vary by several degrees. M. Regnault thinks that this

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