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Beginning with No. 3064, to be published on January 3, 1919, the CHEMICAL NEWS will again appear weekly, and the dates of expiration of subscriptions will be adjusted accordingly.

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DOG FISH LIVER OIL.

By A. CHASTON CHAPMAN, F.I.C.

IN connection with a tehnical inquiry on which I am engaged it has been necessary to submit the liver oil of the dog-fish to a chemical examination, and as very few references to this oil occur in chemical literature, I have thought that it might be of interest to place some of my

results on record.

The common dog-fish (Squalus acanthias)-sometimes less correctly designated Acanthias vulgaris-occurs in very large numbers off various parts of our coast at certain periods of the year. It is readily distinguished from other species by the sharp spines (triangular in section) which occur in front of each dorsal fin, the one before the second dorsal being longer and more conspicuous than the other. It is owing to these spines that the dog-fish is frequently known as the "spur" or "piked" dog-fish.

The dog-fish is viviparous, the mature female producing each season about ten young, each from 9 to 10 inches in length. It is usually found near the coasts during the warmer months, and during the winter it retires into deeper water. The dog-fish varies somewhat considerably in size, occasionally attaining a length of about 4 feet. In weight it varies from 3 to 8 or 10 pounds.

For the purpose of my inquiry a considerable number of the fresh livers were submitted to me, and also two of the freshly caught fish. One of these weighed about 3 pounds and the other nearly 6 pounds, the liver of the former weighing 4 ounces and that of the latter 6 ounces. The largest liver which came into my hands weighed 7 ounces. When the fresh livers were finely minced and steamed, a quantity of oil corresponding with from 40 to 50 per cent of the weight of the livers was obtained, consisting of a pale yellow oil having a slight fishy but not unpleasant odour. When cooled down to about 10° C. it became semi-solid, owing to the separation of a crystalline substance, but regained its transparency on warming. The following results obtained by Thomson and Dunlop are quoted by Lewkowitsch ("Chemical Technology and Analysis of Oils, Fats, and Waxes," ii., 370) :

Two specimens of oil prepared in my laboratory from different batches of liver gave on examination the fol lowing results:Specific gravity (15°/15° C.) Saponification value Free fatty acids (as oleic Iodine value (Wijs)

acid)

Unsaponifiable matters Refractive index at 20°

C.

Brominated glycerides

"No. 1."

"No. 2."

O'9175

o'9186

161.0

168.3

123'3

123'0

0'33 per cent 32'94

O'42 per cent 9'48

insoluble in ether Optical activity (100 mm. tube, sodium light) .. Both the above samples of oil had been cooled to -10° C. for a considerable time and filtered through fine linen, in order to remove the crystalline matter which separated. This was found to contain only 7.3 per cent of unsaponifiable matters, so that it evidently consisted chiefly of glycerides.

It will be seen that the results for the "No. 2" oil agree very closely with those obtained by Thomson and Dunlop. The percentage of unsaponifiable matters in the "No. 1" oil is, however, very much higher, and assuming, as I have every reason to believe, that all the livers submitted to me were from the spur dog fish, it would appear to indicate that the percentage of unsaponifiable matter in this oil is subject to wide variations. At the present moment the precise physiological relationship between unsaponifiable matters and glycerides in the livers of fish is not known; but as these two classes of compounds must be in a constant state of change, and are doubtless dependent on the age and condition of the individual fish, such differences are only what one might expect to find. I am taking steps to obtain a sufficient quantity of the unsaponifiable matter of this liver oil, and hope to be able to submit it to a thorough examination, chiefly with the object of ascertaining whether it contains the hydrocarbon "spinacene," which I have shown to be present in the liver oils of certain fish belonging to the same natural family. Obviously, however, it cannot contain much.

These two samples gave the following colour reactions :

One drop of a mixture of 1 Deep violet, rapidly turning volume of oil with I brown. volume of carbon disulphide was introduced into concentrated sulphuric acid.

As soon as a small quantity of liquid condenses at H the condensing chamber is sealed by it, and it is impossible for the smallest quantity of vapour to escape condensation. The pressure in a forces the liquid by the tube в into the receiver c, which is open to the atmosphere only by the small-bore tube E in order to minimise loss of volatile liquid by evaporation.

This arrangement has been proved very efficient in the distillation of ether residues.

GAS BUBBLER FOR GAS ANALYSIS. By O. D. BUrke.

In estimating sulphur dioxide in gases the general method is to pass the gases containing SO2 to be estimated through a solution of either N/10 iodine or N/100 iodine. The apparatus employed being a flask or bottle connected to an aspirating bottle containing water, the displacement of which is the measure of the gas passed through the apparatus.

The bottle containing the iodine solution is fitted with a narrow glass tube dipping into the iodine solution, or else a tube blown out at end to a globular shape and perforated with fine pin holes, which tend to break up the gas stream into small bubbles.

This method has serious drawbacks, especially in the

A, Condensing Chamber; B, Delivery Tube; c, Receiver;
D, Connection with Distilling Flask; G, Jar for cooling
water; H H', Condensed Liquid; K K', Condensing Water
Supply and Discharge.

water. The tube D is connected with the distilling flask by an air-tight joint. B reaches nearly to the bottom of A, and connects with the receiver c. A stream of cold water is kept running as shown into G, and when it reaches the top of the jar it siphons over by the bent tube x without overflowing the lip of the jar.

hands of careless juniors, where gases which are to be estimated are under pressure. The chief cause of trouble is the tendency to rush the gas through the iodine solution too quickly for the interaction between the SO2 and iodine to be complete, with consequent erroneous results. A variation of as much as I per cent can be made quite easily by careless manipulation by two different juniors. To overcome this difficulty I had a bubbler made (see sketch).

A narrow glass tube is drawn out at one end into a very fine capillary, which is ground level at the point or end. Another glass limb is fused on to the straight limb, and extends downwards to just beneath capillary, where it is flattened out and the top surface ground. The capillary is made to fit tight on the flat ground surface of the second limb.

In this way the gas passing through the capillary tube is broken up into very fine bubbles no larger than a pin point; also the space is so restricted for the passage of the gas that no rushing through can take place, and the time

Interval for the passage of a certain volume of gas is identical in all cases; thereby with just ordinary care ensuring extreme accuracy.

ARSENITE TITRATIONS OF PERMANGANATE

SOLUTIONS.

By ALOKE BOSE, Assoc. Inst. M.M. (Lond.).

WHEN steel is dissolved in dilute nitric acid, and then boiled with the usual quantities of silver nitrate and ammonium persulphate, and the permanganic acid thus formed titrated with a standard solution of sodium arsenite or arsenious acid, it is found the quantity of sodium arsenite or arsenious acid required to titrate the permanganic acid is just about two-thirds of that required theoretically. In other words, the factor obtained for manganese in practice is about one and a-half times as much as the theoretical factor.

The present author came across the above curious chemical phenomenon about three years ago, and though numerous experiments were carried out no explanation could be found, and so the above facts with some figures obtained were communicated to Mr. F. Ibbotson, of Sheffield, on June 15, 1917. Postal communication between India and England is uncertain in these times, and it is quite possible the letter did not reach its destination. Anyhow, no reply came, but an extract of a paper on the subject in the CHEMICAL NEWS by Mr. Ibbotson appeared in the Journal of the Society of Chemical Industry on May 31, 1918. With some difficulty a copy of the paper in the CHEMICAL NEWS (1918, cxvii., 157) was obtained by the present author.

It has been remarked in that paper that the phenomenon above referred to was not generally known, but no serious attempt has been made to explain the cause of it.

There are three points that have been particularly noted by the present author, and they will be discussed in due

course.

1. "The fact, however, that when sodium arsenite is used in the titration of permanganic acid containing free nitric acid the ' oxygen exchange' is not quantitatively expressible by

2Mn2O7+5A$203 → 4MnO+5As2O5, &c."

2. "From these results it appears that solutions of sodium arsenite have a reducing value approximately 33 per cent in excess of the true value, when added to solutions of permanganate acidified with nitric acid. This result is obviously due to the formation of manganic compounds,

3. "The constancy of the ratio of the volume of per manganate to that of arsenite in the second series points to the existence in the solution of a definite compound."

With regard to the first point it might be pointed out that all the errors of the method the present author can think of tend to be in the direction opposite to that found in practice :

(a) During the sodium arsenite titration the colour of the permanganate comes back,

(b) If the free nitric acid in the permanganate solution at all oxidises the arsenite solution.

According to either of the above more arsenite will be required in practice than that required theoretically.

It was the second point, i.e., less arsenite being required in practice, that was noticed by the present author, and as no explanation could be found it was communicated to Mr. Ibbotson.

With regard to the third point, it is not stated whether the "definite compound" exists in the arsenite solution or in the permanganate.

All these points will be discussed more thoroughly after some of the results obtained by the present author are given.

I. (a) When steel is dissolved in ammonium persulphate and water only a clear pink solution is not obtained even when 10 grms. of the persulphate is used for o'z grm. of steel.

(b) If now 10 cc. of 5E nitric (made by adding 690 cc. H2O to 310 cc. strong nitric) be added to the above solution a clear green solution is obtained. If then 5 cc. of silver nitrate (8.5 grms. in 2 litres) be added and boiled a clear pink solution of normal depth of colour is obtained; i.e., it takes the usual quantity of arsenits to titrate (0.33 grm. As406+ Na2CO3, 2 grms., boiled with H2O and made up to 1 litre).

II. When o'2 grm. steel (0.65 per cent Mn) is dissolved in 6 to 8 grms. of ammonium persulphate, water, and 5 cc. silver nitrate, a clear pink solution of normal depth of colour is obtained.

III. (a) When o'2 grm. of steel is dissolved in 10 cc. 5E nitric, and then ammonium persulphate (4 to 15 grms.) be added and boiled, no pink coloration is obtained. If now the usual quantities of silver nitrate and ammonium persulphate be added and boiled, pink colour to the normal extent is produced.

III. (b) If o 2 grm. of steel is dissolved in 10 cc. of 5E nitric, and then boiled with 5 cc. AgNOg and about 4 grms. ammonium persulphate, after dilution (the usual method) normal pink colour is produced. This can be discharged by adding an excess of 5E nitric to the boiling solution, but the colour again returns to its normal extent on standing.

"

IV. When o'2 grm. of steel was dissolved in 10 cc. 5E nitric, with varying quantities of silver nitrate (from 5 cc. to 20 cc.) and 4 grms. ammonium persulphate, pink colour to the normal extent was produced in each case.

V. When o 2 grm. of steel was dissolved in 10 cc. 5E nitric, and then boiled with the usual quantities of silver nitrate and ammonium persulphate, and the normal colour thus produced titrated with standard solutions of ferrous ammonium sulphate and permanganate (as by the bismuthate method), after dilution o 66 per cent Mn was found in a o 65 per cent steel. This should show that all the manganese is oxidised to the condition of permanganic acid.

VI. A standard solution of potassium permanganate was prepared so that 12 cc. of it was equal to 0.66 per cent Mn.

=

.. 24 cc. of it o'66 per cent Mn (when calculation is

made as on o‘2 grm.).

VI. (a) Took o'I grm. steel (=0.325 per cent Mn), and 12 cc. KMnO4 solution (=0.33 per cent Mn) with 10 CC. 5E nitric, 5 cc. AgNO3, ammonium persulphate, &c.

(b) Took 24 cc. KMnO4 (=0.66 per cent Mn) and the usual quantities of 5E nitric, AgNO3, persulphate, &c. In each case pink colour to the normal extent was produced.

The quantities of steel and KMnO4 were then made to vary, but invariably the same factor was obtained.

(c) If 10 cc. 5E nitric, 5 cc. AgNO3, and about 4 grms. persulphate be boiled with H2O till clear, a drop of KMnO4 (N/20) produces a pink colour.

VII. A standard solution of H3ASO3 was prepared (0'33 grm. per litre).

This solution was tested against iodine and found to be of same strength as N/150.

A normal solution of HMnO4

= 11 Mn/litre.

H3A8O3

49 48 As406/litre. .. 49'48 As406 = II Mn. .. 033 A$406 (= 1000 cc) = 0.073 Mn. .. I CC. = 0.000073 Mn

weight).

... I CC.

=

0.000073 Mn =

0'0073 per cent Mn (on unit

o'c36 per cent Mn (calculated

on o'2 grm.). In practice I cc. H3ASO3 = 0.054 per cent Ma (on o‘2 grm.), (see VIII.); i.e., the factor in practice is one and a-half times the theoretical factor.

The As406 solution (theoretically and against iodine) = N/150.)

VIII. Take o2 grm. steel (0.65 per cent Mn) in 10 cc. 5E, and usual quantities of AgNO3, persulphate, &c. Pink colour te the normal extent thus produced was titrated with standard H3ASO3 solution. (Factor=0'054). IX. Take o‘2 grm. steel in dilute H2SO4, add AgNO3, persulphate, &c. Normal pink colour was produced.

X. Take 1 grm. steel and treat as for bismuthate method, make up to 250 cc., and then take 50 cc. (=0'2 grm.), and titrate with sodium arsenite. Normal pink colour was produced.

XI. If a solution that has been treated as for persulphate method be allowed to stand long enough after titration, so long as there is a sufficient excess of persulphate, pink colour to the normal extent returns, and may again be titrated and the same figures obtained.

It will be seen from the above experiments that the different elements used in the persulphate method were eliminated so as to find the interfering element, if any. But none was found. Some of the factors were found to be slightly above and some slightly below o'054, but none of them in any way approached the theoretical figure 0'036.

We shall now return to the discussion of the paper by Mr. Ibbotson as sketched out in the beginning of this paper.

In 1 and 2 special mention has been made of permanganate solution in "free" nitric acid, as if that acid were in any way responsible.

The nitric acid theory was advanced to the present author by Dr. P. C. Ray, of the University College of Science, Calcutta, as early as April, 1917, but Experiments II. and IX. should clearly show that that acid cannot be responsible.

If nitric acid does have any action, then sulphuric acid, or ammonium persulphate plus silver nitrate, must have a similar action and to the same extent. In that case the action must either be a reducing one on permanganic acid, and hence make the latter use less sodium arsenite than is theoretically required, or it must have a reducing action on the sodium arsenite (somewhat similar to that of H2O2 on permanganate).

Neither of the above explanations can hold good. If HNO3 reduces a part of the permanganate then (1) it is not possible to titrate the full amount by ferrous ammonium sulphate (see V.); a permanent pink colour would probably not be produced with traces of permanganate -see VI. (c); (3) titration in solutions where no HNO3 is used should give factors approaching the theoretical.

If HNO3 has a reducing action on the sodium arsenite, which in itself is very difficult to conceive, then when no HNO3 is used the theoretical factor should be obtained, or when varying quantities of HNO3 be used (see III. b) different factors should be obtained.

The above should clear the first point that the "free" nitric cannot be responsible for a higher factor in practice. With regard to the second point, Mr. Ibbotson says that the result is obviously due to the formation of manganic compounds. But what these compounds are and whether they are formed during the oxidation or titration is not clearly stated.

If during the oxidation, then these compounds must be in a lower state of oxidation than HMnO4, and also the same compounds are formed during the bismuthate oxidation, as in both cases the same figures are obtained (see X.). This is not possible. If during the titration, then the manganic compound would come down and render the solution turbid, and a second titration as in Experiment XI. would not be possible.

(N.B.-If a solution with HNO3 be over-boiled in the first instance a precipitate-probably of manganic oxidecomes down, and is not cleared even when boiled with AgNO3 and persulphate).

As for the third point, if the "definite compound" exists in the sodium arsenite then it also exists in the arsenious acid solution. This is not possible, as pure arsenious acid cannot contain any other compound.

On the other hand, if the "definite compound" exists in the permanganate then it means that only a part of the manganese is oxidised to the condition of HMnO4. This also, as pointed out above, is not possible. If it is possible then all the formulæ for the bismuthate as well as for the persulphate methods want overhauling.

Some other explanation must be given. It is quite possible that some complicated reactions take place during the titration, as up to that point it is quite clear from ferrous ammonium sulphate titrations that all the manganese is in the condition of permanganic acid, and the experiments without the nitric acid should show that that acid cannot in any way be responsible for the higher factor obtained in practice.

The Government Laboratory, Sakchi, via Kalimati, B.N. Rly., India, August 29, 1918.

NOTES ON ISOTOPIC LEAD.

By FRANK WIGGLESWORTH CLARKE, United States Geological Survey, Washington.

ONE of the most remarkable discoveries in the field of radioactivity bas been the fact that the elements of highest atomic weight, uranium, and thorium, are unstable, and undergo slow transformations into other substances, especially into helium and lead. The lead thus produced is identical with normal lead in its spectrum and its distinctively chemical properties, but different in its atomic weight; and this difference, which is thoroughly established, is of peculiar significance. The purest lead from uranium minerals has an atomic weight fully a unit lower than that of ordinary lead, while that from thorium minerals is nearly a unit higher. These are the extreme differences, so far as the present evidence goes; but the actual determinations of the atomic weights of these isotopes of lead show wide variations due to differences between the minerals from which the lead was obtained. Furthermore, these isotopes differ from ordinary lead in specific gravity; one being lighter and the other heavier than ordinary lead, these differences being proportional to the variations in atomic weight. Consequently the three kinds of lead have the same atomic volume, and Occupy the same place in the periodic classification of the chemical elements.

Ordinary or normal lead differs from isotopic lead in one important respect, namely, its atomic weight is constant, and the actual determinations vary only within the limits of experimental uncertainty. This constancy was established by Baxter and Grover (7. Am. Chem. Soc., 1915, xxxvii., 1027), who studied lead from a number of distinct sources. Their material was derived from four mineral species, galena, cerussite, vanadinite, and wulfenite, and also from commercial lead nitrate. Furthermore, the minerals examined came from seven widely separated localities; two from Germany, and one each from Australia, Missouri, Idaho, Washington, and Arizona. The lead in each case was carefully purified, and converted into chloride, with which the determinations of atomic weight were made. The method of determination was the standard method long in use at Harvard, and based upon large experience and the most thorough technique. The values found for the atomic weight are shown in the following table :