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JANUARY, 1889.

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DETERMINATION OF THE MELTING POINTS OF SOAP-THICKENED

OILS.
By W. F. K. Stock, F.C.S., F.I.C.

(Read at Meeting, November, 1888.) DURING the last six months the writer has been engaged in the production of soapthickened oils. Correct determinations of melting points was a matter of the first importance, but the presence of soap rendered the ordinary methods of working impracticable. The melting points of many samples range far beyond the temperature of boiling water, and the effect of a heat much below the actual melting point is to cause the liberation of a small portion of the oil and entirely vitiate the results of either adhesion or gravitation processes.

Constant readings are obtained by operating as follows :-A clean narrow test-tube is fitted to a thermometer by means of a short length of hard rubber tubing. The space between the walls of the test-tube and the thermometer must not exceed the sixteenth of an inch. The test-tube is passed through a hole in a cork, and this fits the mouth of a wider and longer tube. A little of the sample to be tested is taken upon the bulb of the thermometer, which is then thrust carefully into the narrow tube to within half an inch of the bottom.

The whole arrangement is now suspended so that the wider test-tube is sunk to nearly its entire length in a beaker of clear lard oil. The beaker stands upon an iron plate over a Fletcher Argand lamp-a little manipulation of the gas supply ensures a gradual and regular rise of temperature. The tubes are brought up to the side of the beaker, so that the observation may be taken by aid of a hand lens. The true melting point is accepted as that at which the mass flows down to a clear bead at the bottom of the tube. The writer has obtained exactly concordant results with oils containing 20 per cent. of soap. The accompanying sketch will serve to make the details clear.

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THE PRESERVATION OF MILK SAMPLES.

By H. DROOP RICHMOND.

(Read at the Meeting, November, 1888.) The preservation of Milk Samples is most important to public analysts ; a milk analysis must be commenced immediately on receipt of the sample, and after the analysis is finished it is not possible to check the results if required, nor should the analysis be disputed, can the sample be referred to another analyst.

Allen (ANALYST, XI., 203) has devised a process for the preservation of milk samples by means of alcohol, but as a large quantity of the preservative must be added, very much depends on the exactness of the proportions, and it is doubtful whether the analysis of a sample so preserved would be of any value in a law court.

It is, of course, apparent that as small a quantity as possible of the preservative should be added. Besides carbon bisulphide, and ether, which were used by Hehner, I have tried the preservative action of dichlorophenol, chloroform, terpenes, and hydrofluoric acid ; none of these except hydrofluoric acid proved wholly satisfactory; chloroform, which kept the milk in a fluid state, and the fat in an easily miscible con

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dition, being perhaps the most unreliable ; carbon disulphide kept the milks fluid, but allowed the cream to rise to form a cake at the top, which could not easily be mixed again ; dichlorophenol preserved the milks fairly well, but the cream rose ; ether and terpenes were of very little use; hydrofluoric acid, of which ·5 per cent. was added, or one drop to 10 c.c. of milk, preserved the milks almost perfectly; of course it precipitated the casein, but a vigorous shake brought this into so finely a divided state, that sampling was quite easy, the fat being evenly mixed; there was not the slightest blackening of the total solids after preservation, showing that decomposition had not taken place; the fat was estimated by Adams' method (Thomson's modification), there being no difficulty in pipetting 5 c.c. on to a strip of paper, which absorbed it fairly well; in some cases it was necessary to add, after putting the milk on the paper, a few drops of ammonia, and to mix the milk and the ammonia with the stem of the pipette, which was afterwards wiped on a dry portion of the paper; the ash was taken in many cases before and after, and was found to have increased about •1 per cent.

A table of analyses is subjoined.
No. Days kept. T. S. Orig. T.S. Presvd. Diff. Fat Orig. Fat Presvd. Diff.
1. 183
8.53 8:57

2:27 2:21

- .06 347

8:57
2.
49
12.60 12.60

4:16 4:07

-.09 145

12:32 _.28 3. 73

12:56 12.50 -.06 3:58 353 - .05 4. 45

13:36 13:17 -:19
5. 38

11.00 11.09
6.
39

11.56 11:50 - .06 3.23 3:20 -:03
7.
34

13:19 13.15 --:04 5.24 5.27
8.
34

13.24 13:35
9.
34

11:45 11:40 - .05 10. 32

11.46 11:50 11. 32 12 03 12:04

4:03 3.96 -.07 12. 32

9.77 9.84 Av.

11:56 11:54 -.02 3.75 3.71 - .04 The whole of these milks were quite fresh when preserved; the following on the contrary were already three days old, when the hydrofluoric acid was added, and many had begun to turnNo.

Days kept. T. S Orig. T. S. Presvd. Diff.
13.
30

12.97 12.82 - •15
14.
31

12.65 12:77
15.
31

14:56 13.84 - 72
16.
31

12.92 12.82 -:10
17.
31

13:33 13.27 -:06
18.
31
12:52 12:04

-.48
19.
32

12.30 12.55
20.
32

12.84 12.23 -51
21.
32

12-51 12.65 22. 32

12.72 12.58 - 14 These last samples were evidently decomposed, they smelt bad in many cases, were curdled in a much more lumpy state than the others, and in several fungus could be perceived.

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In the first series, Nos. 1 and 2 after being analysed when preserved, were sealed up again, and kept for a further period; in both cases there was a blackening of the total solids, indicating that some decomposition had set in; this, and the facts that the ash increases, and that the total solids are not blackened when freshly preserved with hydrofluoric acid shows that the bydrofluoric acid disappears as such.

To further test this question a sample of milk was preserved when fresh ; another portion was allowed to stand for three days, and then preserved; both samples were again analysed after the expiration of a fortnight, with the following results.

T. S. Orig. T. S. Preserved. Diff. 23. Milk fresh

11:32 11:40 24. After standing 3 days, without hydrofluoric acid 11:07 10.70

-37 This shows that hydrofluoric acid only exercises a preserving action when added while the samples are fresh; if decomposition has commenced it is of very little use.

I would recommend that a portion of all milks it is desired to preserve, be taken on receipt of the sample, '5 per cent. of hydrofluoric acid be added, and the bottle securely sealed; no correction need be made for dilution of so small a quantity of liquid, as the difference is well within the experimental error.

The antiseptic power of fluorine compounds was pointed out by W. Thomson in : paper read before the British Association last year.

In conclusion, I must express my obligation to Mr. Hehner, in whose laboratory these experiments were carried out, for his advice and kindly interest in the work. The Laboratory, 11, Billiter Square, E.C. November 14th, 1888.

DISCUSSION. Mr. Davies said he thought the suggestion was decidedly valuable. He would be glad to know whether by the statement that one-half per cent. hydrofluoric acid should be added to the sample it was intended to add the ordinary acid of commerce in this proportion, or such an amount of this solution as would give one-half per cent. true acid in the resulting mixture.

Mr. Blount asked if the acid would have any corroding effect on the glass vessels employed

Dr. Vietu said he was rather adverse to any tampering with samples, and it would be tampering if one-half per cent. of hydrofluoric acid or anything else were added. They would not like an inspector to add the acid, and if added, when the sample came into the hands of the public analyst it would have nothing to do with the sample kept for reference. He did not think a public analyst would recommend the addition of even a small proportion of acids.

Mr. Henner said that some time ago he brought some experiments before the Society and the same point was raised as to the desirability of preserving milk samples. No doubt it was very undesirable to give inspectors power to add anything to samples, and Mr. Richmond was adverse to that; but in the laboratory, and especially during the summer, it was much better in emergencies to be able to preserve samples without fear of their going bad than not to be able to do anything at all. He certainly thought that every sample which was condemned by the public analyst should be kept by him for reference. Not that portion which might go to Somerset House, as they had nothing to do with that, but their own sample should be preserved. He had seen all these experiments of Mr. Richmond's—the milk was curdled by the hydrofluoric acid

but a good shake produced a perfect emulsion. There was no difficulty whatever in analysing it. In the experiments which he brought before them a year ago, in no case was the milk so old as those of Mr. Richmond's.

Mr. Richmond in reply, said the hydrofluoric acid he used was the ordinary acid of commerce, and that he added •5 per cent. of that and not of the actual hydrogen fluoride. As regards Mr. Blount's question referring to the corroding effect of the acid on the vessels employed, he was not quite certain—if he meant had it any corroding effect on the glass bottles in which the milk was kept-he believed it had ; but if he meant the porcelain basins used in the analysis, it had not. The weight of the basins after being cleaned out was exactly the same as before. As regards Dr. Vieth's objections, they had been answered by Mr. Hehner, with whose remarks he agreed.

[NOTE.—We have received the following from Dr. VIETH :-In the remarks which I made in the discussion on Mr. H. D. Richmond's paper “On the Preservation of Milk Samples," I have hardly done justice to this paper. Having fixed my mind upon one particular point, I must confess that in the discussion I lost sight of others. I am very strongly and most decidedly of opinion that official samples kept for reference should not deliberately be materially altered in their composition, not even for the sake of increasing their keeping qualities. But that does not exclude in other instances the employment of a convenient method for preserving milk samples in a state which allows their analysis to be deferred to a future time without interfering with the correctness of the results. Looking at Mr. Richmond's experiments, I freely admit that his suggestion, i.e., preserving milk samples by the addition of a small definite quantity of hydrofluoric acid, is very valuable, and seeing that he has obtained exceedingly well-agreeing results in samples when analysed fresh and after having been kept for weeks, and even months, certainly one which is worth trying by analysts who in their private practice may receive milk samples with which they cannot deal at once.]

ON SOME ABNORMAL SAMPLES OF BUTTER.

BY ALFRED H. ALLEN.

(Read at Meeting, December, 1888.) In July last a sample of butter was condemned by a Public Analyst as being adulterated. The case was referred to Somerset House, and the chemists there, after enquiring as to the terms of the report of the Public Analyst, confirmed his certificate. The butter in question was shipped to England from Copenhagen, but was not of Danish origin, the dairy being that of Kjellstorp, near Wernamo, in Sweden. On learning that the

, butter had been condemned, the shipper sent a sample of butter from the same dairy to Professor V. Stein, the official analyst to the Danish Government. At the same time he took measures to have the dairy visited by the King's Bailiff and the British ViceConsul, who went there and examined everything in and about the dairy, and also interviewed the owner and persons employed in the dairy, all of whom swore that no adulteration of the butter had ever taken place. In due course Professor Stein reported that the sample sent him contained so small an amount of volatile acids as to justify him in calling into question the genuine nature of the butter.

At his request the King's Bailiff again proceeded to the dairy to see the butter made and to take samples of it. He watched the process of churning and working the butter in the presence of a representative of the British Vice Consul, and, as the result of the subsequent analysis, this sample of butter was found to have characters practically similar to those previously observed in the butter sampled in Copenhagen and in the butter condemned in England, some of which had been sent to Professor Stein.

On learning the history of the sample of butter from the dairy, Professor Stein was led to doubt how

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