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acid, will be nothing more than a solution of pure acetic acid LESSONS IN CHEMISTRY.-No. XXIX.
(vinegar) in pure water.
The completeness with which oxalic acid, or, still better
Proceeding with our examination of oxalate of lead, it admits
Extraction of Melallic Lead from Oxalate of Lead. If oxalate
solution of muscovado or common yellow sugar, about the Sulphurous Acid as a Precipitant for Lead. The suffocating gas strength of one of sugar to six of water (both by weight). generated when brimstone or sulphur is burned in atmospheric Solution having been effected by means of heat and agitation, air or oxygen, and termed sulphurous acid gas, is a complete add to it portions of solution of acetate of lead, or, still better, precipitant for lead out of its solutions, and is extensively used the tris-acetate, * commonly known in druggists' shops as for that purpose in the operation of refining sugar by sub-Goulard's extract, until most of the colouring matter has become acetate of lead.
deposited. I say most, because the latter portions of colouring For the purpose of illustrating this action, prepare a solution matter cling to the sugar solution with great obstinacy, and of acetate of lead, strength immaterial, and lighting, imme- cannot be gotten rid of without the expenditure of more scetate diately above the surface of this solution contained in a test- of lead than is from motives of economy desirable. You will
glasa, a brimstone match, blow the gaseous result of combus- observe that on now filtering the sugar solution thus treated, tion (sulphurous acid gas) down upon the surface of the acetate the filtrate will be almost devoid of colour, hence the acetate, solution. These directions being followed, a copious white or rather the tris-acetate of lead would be the very best subprecipitate will immediately appear; the white substance stance, could it be safely used, to be employed for the purificabeing sulphate of lead. The plan we have followed for render- tion of yellow sugar. It is quite evident, however, that the ing evident the effect of sulphurous acid on solutions of lead, employment of this material must remain out of the question is necessarily different from the plan followed in practice until the discovery of 'some inexpensive, readily-applied and whether in the laboratory or the larger scale of commercial unfailing plan of extracting superabundant lead" has been manufacture. The sulphurous acid requires not merely to be devised. All the ordinary precipitants for lead had been tried brought into contact with the surface of a liquid, but to be without avail, until Dr. Scoffern bethought himself of sulphurpassed through it in a stream. On the large manufacturing ous acid, which answers, completely. The process has now scale, the sulphurous acid generated by the combustion of been in extensive operation for more than six years, and no sulphur in atmospheric air is forced through
the liquid to be untoward accident has occurred from the use of the poisonous deprived of lead by means of a pump. In the laboratory, agent. pressure can be more readily obtained by generating the acid This is a convenient opportunity for the introduction of in a flask, a process which no longer admits of burning sulphur some remarks on chemical nomenclature, having special as the source of sulphurous acid. We must employ for this reference to the compounds of oxide of lead with acetic acid, purpose oil of vitriol, and generate our gaseous result by heat- and of very general application in other cases. You will ing that liquid in contact with charcoal, or mercury or copper; remember that I denominated the Goulard's
extract employed in general terms charcoal is the most convenient.
in our sugar refining experiment by the name of tris-acetate or Into a Florence flask, pour about a table-spoonful of wood sub-acetate of lead ; let us therefore investigate the meaning charcoal broken into small pieces, but not powdered, to this of those terms. Tris is evidently a prefix
signifying three of add about a table-spoonfull of oil of vitriol,
adapt a cork and something;
sub is a prefis which means an under or diminished bent tube as represented in the accompanying diagram, fig. 26, quantity of something. We will proceed to i: vestigate the dip the free end of the tube to the bottom of a test-glass con- exact meaning of these terms. Beginning with sugar of lead, taining acetate of lead solution, and apply heat.
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 e, 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 PbO. removed from the solution, which, if exposed for some days to a warm atmosphere, in order to get rid of lingering sulphurous
• Otherwiso called sub-acetate, or Goulard's extract, VOL. V.
Again, Ā is the contracted • symbol for acetic acid; there
And this is man:-Oh! ask of him, fore PbO +Ā or Pb O, Ā represents neutral or mono-acetate
The gifted and forgiven,of lead. But it so happens ihat there are other acetates of
While o'er his vision, drear and dim, lead, in number somewhat doubtful, perhaps five or six, all of
The wrecks of time are driven ; which contain an excess of base (oxide of lead, or PbO).
If pride or passion in their power, Indefinitely therefore they may be generalized as sub-acetates
Can chain the time, or charm the hour, of lead; but if we desire to be precise, and indicate what kind
Or stand in place of heaven: of sub-acetate of lead any particular one may be, we must have
He bends the brow, he bows the knee, recourse to numeral prefixes, and chemists have long agreed
“Creator, Father! none but thee !" 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- ON PHYSICS, OR NATURAL PHILOSOPHY, salt generated by combination of three of base with one of acid,
No. XXX. and so on for the rest. Furthermore, it should be remarked, that, in addition to the general or indefinite word sub-salt,
CALORI C. there is another very much employed in modern chemical
Continued from page 36.) treatises : I mean basic salt; that is to say, a salt in which the base predominates.
The following table will be found of great utility in convertIn our next lesson we shall enter upon the important process ing the number of degrees on any of the ihree different scales of cupellation, or separation of lead from silver, and indeed into the corresponding number of degrees on either of the other 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 This table will be extremely useful to Students of Chemistry devoting their attention to the study of the precious metals. 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 table commences with the number of the degrees marked
Fahrenheit, - 41.25 Centigrade, and --33• Reaumur. Thus,
suppose that when the temperature of a body is 2009 Fah.
renheit, and you wish to know what it is on the Centigrade (From the New York Evening Post.)
scale, and on Reaumur's; by turning to the number 200 in the
column headed Degrees of Fahrenheit, you find in the hori. The human mind, -that lofty thing!
zontal line with 200, and in the other two columns to the
right, the numbers 93.33 and 74:66, which indicate that the
ng And breathes his judgment tone.
the Centigrade scale, and 74° -66 on Reaumur's.
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. That lofty thing,—the human mind!
zontal line with 70, and in the other two columns, one to the The human heart,- that restless thing!
left and one to the right, the numbers 158 and 56, wbich indiThe tempter and the tried ;
cate that the corresponding degrues of the given temperature The joyous, yet the suffering, –
are 1589 on Fahrenheit's scale, and oto on Roaumur'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; hy turning to the number 69 in the
column headed Degrees of Reaumur, you find in the horizontal Yet do we blees thee as thou art,
line with 59, and in the other two columns to the left, the Thou restless thing,—the human heart!
numbers 73-75 and 164:70, which indicate that the correspond The human soul,--that startling thing!
ing degrees of the given temperatures are 730-75 on the Centi
grade scale, and 164":75 on Fahrenheit's,
When the proposed number of degrecs 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 thermo.
mewr, was 600°, and it was required io tind the corresponde
568 letter A with a dash orer it, thus Ã; and here it may be remarked that a dush over a letter siznities the body to be of the organic kingdom, i.e. either of animal or vegetable origin, whereas a dash under an initial is a
9)2845.00 reduplication of quantity. Thus , means acetic acid, and A 2 of acetic acid.
212 211 210 2 210 209.75 209 208.4 208 207.5 207 206.6 206 205-25 205 2018
78.88 78 75 78.33 78 77.77 77.5 77.22 77 76.66 76.25 76.11
58 57.77 57-5 57 22 57 56.66 56.25 56:11 56 55.55
46.4 46.22 46 45.77 45 6 45.33 45 44.SS 44.8
202 2012 201 200-75 200 1994 109 1985 198 1976 197 196.25 196 195 8 195 194 193 192.2 192 19175 191 190.1" 190 189.5
63:11 136.4 63 136 62.66 135.5 62-4
135 62.22 1346 62
131 61.77 133 25 61.6 133 61.33 132 8 61 132 60.88 131 60 8 130 60 44 129 2 60
129 59.55 128-75 59.2 128 59:11 127:4 59
127 58.66 126.5 58.4 126 58.22 125.6 58 125 57.77 124.23 57.6
124 57.33 123.8 57 123 56.88
122 56.8 56'44 120.2 56
120 55.55 119.75 55.2 55.11 118.4
118 54.66 117.5 54.4 117 54.22 116.6 54
116 53.77 115.25 53.6
115 53.33 114.8 53 114 52.88 113 52.8
111 51.55 110.75 51.2 110 51.11 109.4 51
109 50.66 108.5 50 4 108 50.22 107 6 50 107 49.77 106.25 49.6 106 49.33 105.8 49 105 48.88 104 48.8
103 48:44 102.2 48 102 47.55 101.75 47.2
101 47:11 100.4
143-6 143 142.25 112 14168 141 140 139 138 2 138 137-75
Fahrenheit. Centigrade. Reaumur. Fahrenheit. Centigrade. Reaumur. Fahrenheit. Centigrade. Reaumer. Fahrenhelt. Centigrade. Reaumur.
16.25 16.11 16 16:55 15 14:44 14 13.88 13.75 13:33 13 12:77 12.5 12:22 12 11.66 11.25 11.11 11 10:55 10 9.44
-2.22 -2.5 -277 -3 -3.33 -3.75 -3.88
10.4 -17.5 -10.66 --18
--18.4 -11.11 -19
- 11.2 -19.75 -11:55
--20 -12 -20.2 - 12:44 -21 -12.8 -22 -12:88
-23 -13 -23:8 --13:33
-24 -136 -24.25 -13.77 -25 -14 -25.6 -14.22 -26 -14'4 -- 26.5 --14.66 --27 -16 --27.4 -16.11 -28 --16.2 -28.75 --15.55
-41.8 --21.33 -42 --21.6 -42.25
- 27.22 -21.77
-35 --28 -35-55-28.44 -36
-28-8 -36 11 -28-88 -36-26 -29 --36.66 -29.33 -37 - 29 6 -37.22--29 77 -37-5 --30 -37.77
--30-22 -38 -30-4 -38.33 --30.66
-38.75 -31 -38.88 31.11
-39 -312 -39'44 -31.55 -40 -32 -40-55 -32 41
-32:8 41.11 -32.88 41.25 -33
8.88 8.75 8.33 8 7.77 7.5 7.22 7 6.66 6.25 6:11 6 5.55 5 4.44
3.88 3.75 3.33 3 2.77 2.5 2.22 2
primitive state of aggregation, this explanation being founded
on the supposition that, at the end of two or three years, the Displacement of the Standard Point. - Thermometers, con- fixed point is no longer subject to displacement. But, accord. structed even with the greatest care, are subject to one cause ing to the experiments of M. Despretz, this displacement of error which it is important to observe; it is this : that after appears to continue during a period almost indefinite. Besides a certain time, the standard point, which is zero on the cen- this slow displacement, sudden variations in the position of tigrade, and 32° on Fahrenheit's thermometer, tends to rise, the fixed point have been observed, whenever the thermo: 80 that sometimes it is found out of its place by as much meter has been raised to a high temperature. Indeed, if at as 20 on the former, and nearly 4o on the latter; that is, that time we immerse the instrument in melting ice, the the mercury no longer descends to the fixed point of the scale, mercury sinks no longer to the freezing point on the scale, when the thermometer, is immersed in melting ice. Various and it returns to it only at the end of a certain period. It is explanations of this phenomenon have been given, but none of importance, therefore, when it is required
to measure temo appears to be quite satisfactory. It has been attributed to a peratures with precision, frst to verify the position of the diminution of the volume of the bulb, arising from the effect fixed point in the thermometer which is about to be employed. exists in the thermometer; but it has been observed that ters which are accurate with respect to the two fixed points thermometers which contain air change like those which on the scale, namely, the freezing and the boiling points, are bulb, after it has been blown, returns bat very slowly to its times vary by several degrees. M. Regnault thinks that this
differenee is owing to the unequal expansion of the glass of liquid is introduced into it, in sufficient quantity to fill the
general, sulphuric acid coloured red is employed. The appa-
uil, near Paris, in 1814, invented a thermometer of a similar
Leslie's Differential Thermometer. - Professor Leslie (after. quarters of an inch in length, and zero is marked at each ex-
sufficient to incline the thermometer to one side ; but this is
Breguet's Metallic Thermometer.-A thermometer constructed