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232

Loss of Nitre in the Vitriol Manufacture.

gases, extend to the opposite side of the tube. Hittorf has made known in what manner a magnet acts upon the rays of cathodic light. If the results which he has established are applied to the movements of the rays of negative light, there follow, as necessary consequences, all the movements which are observed in the green light under the influence of the magnet. The form of the luminous surface is quite independent of the form of the side touched by a conductor. It can be directly shown with gasdensities somewhat greater than correspond to the production of the green light that the spot touched by the conductor emits a cathodic light. Over the spot in question are seen spheroidal tufts of blue light. The luminous green surface is merely the basis of these blue rays. The author has shown that the positive and negative light can perfectly interpenetrate each other for spaces of any length.

The intensity of the green light emitted from a point of the side of the tube, if the intensity of the exciting radiation is constant, decreases with the continuance of the excitement. This decrease is the greater the stronger the intensity of the exciting rays and the original brightness of the luminous point.

"If between the cathode and the green luminous side of the tube there is introduced a solid body, its shadow is thrown upon the side, since it excludes such rays of the cathode as impinge upon it from reaching the side. If the solid body after some time is removed, the shadow disappears, but an image of the body remains, distinguished from the surrounding luminous surface by its greater brightness, and exactly reproducing the shape of the former

shadow."

LOSS OF NITRE IN THE VITRIOL
MANUFACTURE.

By JAMES MACTEAR.

It

THE letters which have been published in recent issues of the CHEMICAL NEWS have thrown considerable light on the above subject, but much still remains uncertain. seems to me that it is the duty of those who have studied this subject to make public whatever facts they may have ascertained, so that sound conclusions may ultimately be drawn from a careful comparison and consideration of these facts. With this view I beg indulgence and space for some details of the work I myself have done in this direction, and trust it may also induce others to publish the result of their researches.

Shortly speaking, the losses in the case of good plant might be stated as occurring in two ways:

1. As lost by escaping with the exit gases into the atmosphere.

2. As lost in the acid in the chambers for use (which may or may not have passed through Glovers). If, however, the amount of nitrous compounds in the escaping gases capable of absorption by caustic soda, and the amount of nitrous compounds in the acid used, be estimated, it will be found that these two sources of loss are very far from accounting for the amount used.

In my researches the estimation of the nitrous compounds in the escaping gases was made by taking average samples over twenty-four hours, the aspiration being at a constant rate (a very necessary precaution); and the determining the nitrogen present in the absorbing solution by means of the zinc and iron distillation with caustic soda process-which I showed in a paper read before the Newcastle-on-Tyne Chemical Society, January 24th, 1878gives most accurate results when properly carried out.

These daily average samples were checked by an average for the week, and only in very rare cases was there an appreciable difference from the average of the daily

tests.

The amount of work involved in these experiments is

{CHEMICAL NEWS,

May 30, 1879.

very great, but in my opinion it is only possible to arrive
at just conclusions by a long series of such tests. The
arrangement of these results weekly was as follows:-
Week ending
187

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pyrites used.
nitre 97

O. V.

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arg. oxygen in exit gases.

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grains NaNO3 per cubic foot. vol. per cent NaNO3 in acid used. calculated as NaNO3 on 100H2SO4.

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The figures obtained are embodied in the following table,
and represent the results of seven series of large cham-
bers, all worked with Gay-Lussac towers, and all but one
with Glover towers, the one exception denitrating its aci
by hot water in a long tunnel. (See Table on next page.)
It will be seen that the unaccounted for loss has never
been under 50 per cent of the nitre used, and in one case
has reached go per cent, which is not explained by the
percentage of nitre used on sulphur, as we have-
Week No. 13, 52.6 per cent of nitre
No. 23, 90'43

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The total nitre used being

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=

No. 23, 4'236.

2.683 on sulphur. = 3.831

It would seem that the unaccounted for loss is intimately connected with the working of the chambers, as in most cases it is found that where the percentage of nitre used on sulphur is high, so also is the loss of nitre unaccounted for calculated on sulphur.

As yet no one seems to have hit the blot-Where does the loss take place, and under what conditions? Did we know this we should be able to manufacture our acid at a much reduced cost, were we able to avoid this unaccounted for loss, which is at least 2 to 3 per cent on the sulphur. The directions in which I have looked for a solution of the problem are

A. Decomposition of the nitrous gases in contact with hot kiln gas before entering the Glover towers or chambers.

B. In their passage through the Glover tower. C. In their passage through the series of condensing apparatus generally known as vitriol chanıbers. Hitherto my results have been much more of a negative character than otherwise; but a record of failures is of great use, and often leads to a right way out of a difficulty.

I made a number of experiments on a series of vitriol chambers which had no Glover tower, and where during the continuance of the experiments all the nitre was potted in a large pot placed at the end of the row of kilns, all the sulphurous gas passing over it.

The data used in calculating out these experiments in No. 6 series of chambers were

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NEWS

0'452
0'590
I'000

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0350

3448

35.80

2 433 10'0

3 443 9'5

0'940
0 622

4 441 12'0

5 427 10'0 6 440 10'0 7 307 10'0 8 24 10'0 9 440 10'0 10 441 IIO II 461 10'0 12 463 100 13 463 10.0 14 473 II'O 15 470 II'O 16 464 10'4 17 462 11'0 18 470 11'5 19 437 11'5 20 482 115 21 457 II'I

0'779
0'915
I'020

0'796

0117 0613 6:36
1960 4'572 57.84
O'194 1052 1130 0616 3′136 33'70 1840 5'089 54'70 3'000 9'304 100
0102 0'565 5:46 0327 2353
0192 1034 8.61 0'555 3.865
O'220 1175 924 0·600 3.883
0156 0.880 725 0'450 4320
0145 0552 555 0320 3025
Ο ΙΙΟ 0033 055 0.030 0.872

3:180 9.633 100

5'500

5'460

22.70 1362

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O'257

23 454 10'6

0.113

24 475 89

0'432

25 403 9'3

0.368

26 448 10'4

0'236

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1'012
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0'675

7'430 7184 4311 10°348 100 6'000
32.20 2:081 7113 59 20 3.824 12'012 100 6.460
30'54 1990 7657 60*22 3.920 12.715 100 6.510
35.63 2210 6922 57.12 3.560 12.122 100 6'220
30 40 1750 6373 64'05 3.690 9'950 100 5.760
14'40 0700 5'135 8505 4'120 6'040 100 4.850
0*190 1056 12.20 0*700 1953 22.60 1.300 5621 65.20 3.750 8.630 100 5'750
0'093 0'529 600 0°310 3'509 40'20 2060 4'696 53'80 2.760 8'734
100 5'130
0110 0'573 7:00 0*340 2752 33.30 1610 4'940 59'70 2.890 8.265 100 4.840
0075 0463 6:40 0'300 2743 37.80 1770 4052 55.80 2620 7258 100 4'690
0049 0 287 3'40 0173 3710 44'00 2244 4420 52.60 2.683 8.417 100 5'100
0130 0756 10'00 0'460 2.800 37.00 1680 4019 53'00 2:420 7'575 100 4'560
0'061 0.357 5:30 0216 2.682 39.50 1616 3'751 55 20 2 260 6.790 100 4'092
0.012 0.069 129 0420 1543 28.85 0937 3'736 69.86 2.271 5*348 100 3.250
nil nil nil nil 1912 34'00 1185 3714 66'00 2301 5626 100 3'486
nil nil nil nil 1269 23:03 0.830 4248 76:97 2952 5:510 100 3.835
0058 0315 6·73 0258 1212 25.87 0.877 3158 67:40 2255 4685 100 3'390
0043 0'270 803 0224 0659 19:57 0546 2437 72:40 2023 3'366 ΙΟΟ
0039 0 228 536 0170 0783 18.36 0.582 3*247 76 28 2418 4258 100 3'170
nil ni nil nil 0915 17.30 0654 4375 82.70 3128 5.290 100 3.782
0'0066 0036 0'51 0'022 0384 9:06 0383 6.568 90°43 3831 7'290 100 4:236
0'074 0437 682 0240 1506 23:52 0852 4 460 69.66 2:576 6493 100 3.688
0032 0161 2:58 0.093 1301 20192 0753 4763 7652 2759 6·225 100 3.605
nil nil nil nil 0936 14.80 0.533 5.385 85.20 3'073 6.321 100 3.606
nil nil nil 1418 20 63 0745 5'455 79'37 2.866
6.873 100 3611
kilns where the heat was highest 5.63 parts. The differ-
ence, 0.23 part, is very small and is not more than the
error which might be expected in such experiments, so
that in this case I do not think we have proof of a greater
loss of nitre by the decomposition of the nitre at a higher
temperature, at least not to the extent that might be
expected.

The following are the results obtained :-
Loss of Nitre in No. 6 Chambers, working large pot (A).
Ist expt., 24 hours, 31 per cent of nitre used.
2nd
60
99

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3rd 19 53 4th Actual average of 71 days, 60'4 per cent of nitre used. The average NaNO3 used during this time was 9 per cent on sulphur and 60'4 per cent of total, or 5'44 per cent on sulphur has disappeared.

During the same time the gases entering Gay-Lussac contained on an average 3.71 grains NaNO3 per cubic foot, while the amount in the exit gas was o'30 grain, which shows an absorption of 92 per cent. The gases entering Gay-Lussac were aspirated at a regular continuous rate of 0'5 cubic foot per hour. The pyrites was charged at the rate of 8 cwts. per hour, and the nitre charged varied from 30 to 40 lbs. per hour.

The method of working was now changed, small pots being used for the decomposition of the nitre, and these were placed actually on the burning mass of pyrites in the kilns. The following are the results :

Loss of Nitre in No. 6 Chambers, working small pots (B).
Ist expt., 48 hours, 45'3 per cent of nitre used.

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flues or in the kilns that more nitre is used is one that is The fact that when using small pots in the part of the vitriol manufacturers. It seems to me to depend somequite beyond doubt and well known to all experienced what on the fact that at the high temperatures the nitrous compounds are driven off much more rapidly, and sent into the chambers, as it were, in "whiffs" or "gusts instead of in an equally distributed manner; it is more difficult to keep the chambers in good condition, and the

amount of nitre used is therefore increased.

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If we assume that the absorption in the Gay-Lussac be | equal in both cases to, say, 95 per cent of the nitrous compounds entering, then the two cases above detailed would show :

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A. 90 per cent nitre used-5'44 lost=3.56 entering tower.
B. 11.6
-5.63
93
19 =5'97
The loss in exit gases would then be-
A. 0178 per cent on sulphur.
B. 0.298

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And if we take the exit loss in "A" as 100, the loss in "B" would be 167, or the loss by the method of working as in "B" required 67 per cent more nitre than that in A," which is sufficiently convincing as to the inadvisability upon this system.

It would appear, then, that as far as these experiments" go we have lost in the case where the nitre was decomposed in the large pot in the colder portion of the flue 5'44 parts of nitre for 100 of sulphur, and in the case where the nitre was decomposed in the small pots in the

The above experiments, although numerous and interesting, are by no means complete, and more light is greatly wanted.

234

CHEMICAL NEWS

Deviation of Polarised Light by Solutions of Inverted Sugar. (May, 179.

It is pretty clear that there is a very large loss between the Burners and the Gay-Lussac towers; the experiments in No. 6 series of chambers show that the loss was not very greatly increased by the greater heat at which the nitre was decomposed, and at which consequently the nitrous compounds and sulphurous acid began to react upon each other. We are thus shut up to admit a large loss or reduction of nitrous compounds in the chambers themselves, or no doubt where Glover towers are in use, in the Glovers and chambers combined. So far as my results go there is no proof that the loss is greater where Glover towers are in use; it is, in fact, more the other way, for while the loss where no Glover is used amounts to in

Case A, 5'44 per cent NaNO3 on sulphur,

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B, 5.63 the whole series of experiments extending over more than year of weekly testings, the loss when Glovers are used is not more than about 3.5 per cent on sulphur. My own opinion is that the greater regularity with which the nitrous compounds are supplied to the chambers has a great deal to do with the question of loss; but this is a point not yet worked out, so far as I am aware, by any one. The varying statements that one hears made are so contradictory that it were well that those who have trustworthy experiments should publish them, so that by a careful digest and comparison we might come to some valid conclusion. As for myself, I may say that at present I am halting between two opinions, but I trust that experiments now in progress may enable me to decide

either for one or the other.

Mr. Davis, in his letter in the CHEMICAL NEWS, vol. xxxix., p. 216, refers to the escape of nitric oxide and invites chemists to state their views, after which he will give the experiments which he has made on the subject. As a chemist who has failed completely in obtaining reliable means of determining the amount (if any) of nitric oxide in exit gases, permit me to appeal to Mr. Davis as to whether he should not give us these results at once. As one of the Alkali Act Inspectors, Mr. Davis ought I think to give us any information which may enable us to keep down the escape of noxious vapours, to say nothing of the economy of nitre.

I notice from the correspondence generally that the amount of nitrous compounds present in the actual acid run off for use is not well known. It varies a good deal, but the tests in the table show what it has been in my own case, and the following gives details of a number of tests of the works of my firm at Newcastle :

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ON THE INFLUENCE OF
VARIATIONS OF TEMPERATURE ON THE

DEVIATION OF POLARISED LIGHT
BY SOLUTIONS OF INVERTED SUGAR.*
By P. CASAMAJOR.
(Concluded from p. 214.)

THE announcement that it was at 92° that d became equal to 0, led me to think, that, possibly, the law that I had deduced from Clerget's table was not correct. It is true that the temperatures given by Clerget only extend from 10° to 35° C., but, between these limits the law which governs the deviations of inverted sugar as affected by temperature, as deduced from his table, is represented by a right line. This I considered as an important fact, because I do not remember a single instance in which a law is expressed by a rigorous right line, between limits that are sufficiently distant, in which this right line is not continued throughout. Having, then, very serious doubts about the accuracy of Clerget's table, I started to discover what the true law was.

For this purpose I prepared pure sugar, by taking the best cut loaf sugar and soaking it in 95 per cent. alcohol for several hours, taking the sugar out, letting the pieces drain, and drying them by hot air.

This sugar, tested before inversion, gave exactly 100 by the saccharometer. The solution, after the direct test, was inverted and tried again in the saccharometer at several degrees of temperature. After making a great many tests at various temperatures, I was forced to the conclusion that not only is Clerget's table correct for temperatures between 10° and 35° C., but that the law represented byd = −44+.

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held good even beyond 88° C., at which temperature the deviation is equal to 0.

To enable an observer to seize at a glance the results I have obtained, I took a large sheet of cross-section paper divided very accurately into inches and tenths of an inch. On the line of the abscisses I took for every degree Centigrade a space equal to two-tenths of an inch, and, on the line of the ordinates, I took for every division on the negative scale of the saccharometer, four-tenths of an inch. I then drew a right line, connecting the point representing -44 of the saccharometer scale with the point representing 88° C. This right line represents the law expressed by the formula

d=-44+2.

Afterwards I plotted on this sheet 68 observations made at temperatures varying from 14° to 92° C. The result of this operation was that, out of 68 dots, 10 were entirely erratic, 18 were exactly on the line, and the remaining dots were so close that their distance from the line could be explained by an error of of a division in the observation of the saccharometer. In explanation of these results, I may state that the dots which I have called erratic were due to observations made on turbid solutions, or while the temperature was fluctuating. Observations made under such circumstances cannot be expected to be accurate The other observations were made under conditions in

finitely more trying to the eyes than those under which
ordinary saccharometric tests are made. When the tem-
disk of double quartz becomes distinctly elliptical, and,
perature fluctuates in the least during an observation, the
at times, the line of separation between the two quartz plates
swerves alternately to the right and to the left.†

Read before the American Chemical Society, Feb. 6th, 1879.
The sheet on which these dots are plotted was shown to the

American Chemical Society. I have not thought it necessary to have
it engraved, as the explanation given in the text makes the subject
sufficiently clear.

CHEMICAL NEWS,

May 30, 1879) Deviation of Polarised Light by Solutions of Inverted Sugar.

To obtain the different temperatures required for these experiments, I had to alter a saccharometer so as to interpose a water-bath between the two optical portions in a manner similar to that adopted by Dr. Ricketts. At the bottom of this water-bath is an opening, communicating with the interior of a closed tube, three inches long, projecting at a right angle. To the closed end of this tube a Bunsen burner was applied when the water-bath was to be heated. In this water-bath I placed the tube containing the solution of inverted sugar. This tube is made of thin brass, and is closed at each end by a glass plate, held by a screw cap in the ordinary way. In the middle of this tube a portion was cut off, two inches long, and as wide as the diameter of the tube. Over the opening thus formed was soldered a projection, as shown in figures I and 2 at A. At first I used a tube with a cylindrical projection, of the same diameter as the tube itself, for the introduction of a thermometer to ascertain the temperature of the liquid in the tube, in the manner adopted for Clerget's thick glass tube. I think that the plan represented in fig. I and fig. 2 is preferable, as it allows the operator to agitate the solution by moving the thermometer backwards and forwards in the tube. A great advantage obtained by having a projection of this shape is that the

235

the tube was different from that of the water bath, and that the difference between the two temperatures must depend on the rate of heating the water-bath, i.e., on the size of the flame.

I have mentioned that a thermometer with a long bulb may be the cause of serious errors; so may a thermometer whose movements are too sluggish. In the thermometer that I have used, the bulb was very short; the mercury column was very fine, so as to respond very quickly to slight variations of temperature. These thermometers have 40° C. on a scale six inches inches long. One goes from o, to 40°, the next from 30° to 70°, and the third from 60° to 100°. Particular attention was paid in these experiments to keeping the water-bath in continued agitation immediately before taking an optical observation, and while the observation was being made. The thermometer in the brass tube was also kept moving backwards and forward's for some time before looking through the tube. Unless these things are done, there is no certainty that the tem petature observed is that of the liquid in the tube. If, as I am convinced in this case, from the numerous experiments I have mide, observations on solutions of inverted sugar, taken at any temperature, are as reliable as those made at any other temperature, there can be no FIG. I

A

FIG. 2

liquid in the projection does not rise or fall perceptibly when the thermometer is taken in or out. If the vertical projection has small section, whenever a thermometer is placed in it the liquid rises in this projection, and a portion may be high enough to stand above the level of the water bath. Under these circumstances, this portion of the liquid gets cooler than the portion in the horizontal tube, and, if the bulb of the thermometer is longer than the diameter of the horizontal tube, the temperature indicated will be too low. Too much care cannot be taken in observing these minutiæ, as otherwise accurate results cannot be obtained. Even with the greatest care, it is Impossible to avoid errors in the observation of solutions whose temperature does not remain constant. In this connection I may be allowed to express the opinion that it was due to the want of a tube like the one represented in fig. I and fig. 2 that Dr. Ricketts was led to take 92° as the temperature at which d becomes equal to 0. I have repeatedly found at 92° that the deviation is on the positive side of the scale, ranging from 14 to 2, according as the observation was more or less accurately made. In his experiments, Dr. Ricketts did not take the temperature of the liquid in his tube, but that of his water-bath. As his tube was made of glass, about one-eighth of an inch thick, we must suppose that temperature of the liquid in

A

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and it is not certainly worth while to go out of our way for this purpose. The most convenient plan for making observations on solutions of inverted sugar is to follow the directions of Clerget, which are the following:

A sugar solution is placed in the ordinary way in the saccharometer, and the saccharometric test, D, is noted down. To a portion of this solution, say 50 c.c., are added 5 c.c. of concentrated hydrochloric acid. These are mixed by shaking up the graduated flask, and the flask is placed in a water-bath and heated to 68° C., taking about 10 minutes in raising the temperature. This solution is afterwards immediately cooled to a temperature between 10° and 35° C. We then placed it in a thick glass tube, provided with a vertical tubulure for the insertion of a thermometer to show the temperature of the liquid at the moment of observation. This tube is made 22 centimetres long, instead of 20 centimetres, so as to compensate for the the addition of one-tenth of hydrochloric acid. If th

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236

Composition of a Boiler Incrustation.

temperature, at the time of observation, is t, and the deviation to the negative side is d, we take the algebraic difference of the two readings, D-d, which is the arithmetical sum. To find the correct quantity of cane sugar C, from these observations, we must remember that for 100 per cent. of sugar,

Designation
of Sugar.

Raw

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CHEMICAL NEWS,

May 30, 1879.

Saccharometric Test Corrected by Glucose,

Inversion. Copper Test.

(before Inversion).

861

87

85

86

Refined-B

911

92

C

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If we have Clerget's table, we may, instead of making this calculation, follow the practical directions at the head

of the table.

Instead of inverting by heating to 68° C., and then cooling down rapidly, it is advised by some authors that the solution be mantained at 70° for at least 15 minutes. I can say, after doing both things repeatedly, that, in the second case, the solution is no better inverted than in the first. Some persons think it necessary to heat at 70° for an hour. This I did not try, as I had found no advantage in heating 20 mimutes longer than Clerget directs.

For solutions that are to be heated above 68° for experi mental purposes, it is necessary to neutralise the hydrochloric acid by a base, as otherwise the solution becomes very red. For this purpose the preference should be given to carbonate of soda, which gives the best results. I put enough of carbonate of soda to make the solution slightly alkaline, and afterwards make it acid with a slight excess of acetic acid. In this condition the solution may very conveniently be placed in a brass tube. For some reason which I have not been able to discover, when the hydrochloric used in inversion is neutralised by magnesia, the indications of the saccharometer are always too low.

When Venteke's saccharometer is used for testing inverted sugar we are obliged to operate on solutions of greater dilution than the normal solution containing 26'048 grs. of sugar for 100 c.c., because the negative side of the scale is very limited, reaching only to -16 on some instruments. Á solution holding 26.048 grs. of sugar in 100 c.c. is tested directly. Then 50 c.c. of this are transferred to the beaker; the 50 c.c. flask is washed out, and the wash water is added to contents of beaker, and also 10 c.c. of hydrochloric acid. After the solution has been inverted and saturated with carbonate of soda, if necessary, the whole is put in a 100 c.c. flask, and enough water is added so that the whole solution at 15° C. shall occupy 100 c.c. The result of the test, after inversion, has then to be multiplied by 2.

I will conclude by giving from my books a series, 28 consecutive tests of raw and refined sugars. In the second column I give the direct test, before inversion; in the third column, the correct test, as afforded by inversion. In a fourth column I have given the copper test for glucose, when I happened to have it. These glucose tests show that the substances which reduce the alkaline tartrate of copper are, for the most part, without action on polarised light.

Since this paper was read before the American Chemical Society! Dr. Behr has kindly called my attention to a paper of Dr. Tuchschmid in Scheibler's Zeitschrift for 1870, p. 649. After a series of elaborate experiments, Dr. Tuchschmid concluded that Clerget's table was very reliable. He investigated the law of this table between 4° and 41.8° C. Instead of the formula given above, he found

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In the case in which the test before inversion is lower than when corrected after inversion, the presence of an excess of lævo-rotatory substance is indicated. When, on the contrary, the test, before inversion, is higher than after inversion, as in the case of the Manilla sugar, an excess of dextro-rotatory substance is indicated. If these sugars are inverted, and the solutions of inverted sngar are tested in the saccharometer at 88° C., they would show deviations on the positive side of the scale. This, however, does not enable us to decide to what particular dextro-rotatory substance the deviation is due.

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Before committing myself to an opinion as to its cause, I wrote to my clients asking them for particulars of construction of the boiler, and learnt in answer that it was a "hot-water circulating boiler for domestic use," and, further, that the boiler and cylinder were constructed of "galvanised" iron, and communicated the one with the other by means of leaden pipes.

The explanation which I gave of the cause was briefly this-The town water, with which the boiler was fed, and which is soft to commence with, would, on boiling, be rendered still softer, and by constantly circulating

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