minations of specific temperature reaction published by Thomson and Ballantyne,' who have done most toward putting the test upon a satisfactory basis, and those obtained by us as described above and shown in detail in Table III.

TABLE IV.-COMPARISON Of Average RESULTS-SPECIFIC TEMPERATURE REACTION.

With most of the vegetable oils the results obtained by us with the diluted acid are slightly lower than those reported by Thomson and Ballantyne, while with the few animal oils compared our results are a little the higher. In general the agreement between the two sets of results is sufficiently close to indicate that the adoption of the modification here used involves no radical departure from what has heretofore been considered the best practice.

A NOTE ON THE DETERMINATION OF MOLYBDENUM IN

STEEL.'

BY GEORGE AUCHY.
Received January 23, 1902.

P to recently the analyst has not often been called upon to

termination will be frequently made. To steel works chemists

1 Loc. cit.

2 Read at the meeting of the Philadelphia Section of the American Chemical Society, January 16, 1902.

accustomed to determining phosphorus indirectly from the volumetric estimation of the molybdic acid in the yellow precipitate by zinc and permanganate, this would seem to be the easiest and simplest way also of determining molybdenum in steel; first, of course, separating the molybdenum from the iron by ammonia or soda. The point to be settled is: Can the molybdenum be completely separated from the iron by one precipitation with ammonia or caustic soda?

It will be found upon trial that the use of ammonia in only moderate excess, at least, is entirely out of the question. But the following results indicate that caustic soda answers sufficiently well for practical purposes, though not perfectly. Perfect separations by this reagent were, however, obtained by Ibbottsen and Brearly. In these tests the molybdenum was determined gravimetrically in an aliquot part of the filtrate.

In the following, the molybdenum in the filtrate was determined volumetrically-zinc and permanganate.

The writer proceeds as follows: Not more than 1.308 grams of steel are treated with a large excess of strong nitric acid and a little potassium chlorate (if chromium is also present, as is usually the case); the nitric acid is evaporated off, boiled with strong hydrochloric acid, and evaporated to dryness to separate silica; again taken up with strong hydrochloric acid and evaporated to first appearance of scum. Then 5 cc. strong hydrochloric acid, diluted to 20 cc. with water, are added and heated to effect complete solution. The volume of the liquid is made up to 50 cc. and poured, little by little, with shaking, into 20 grams caustic soda dissolved in 100 cc. water in a 12-ounce Erlenmeyer flask, provided with a file mark at 300 CC. The liquid is diluted to this mark and mixed by shaking around in the flask, allowed to settle, and filtered into a 250 cc. measuring flask, until it reaches the mark. Then trans

1 Chem. News, 82, 2137.

ferred to a beaker, acidified with sulphuric acid, boiled down to less than 100 cc., and finished as in phosphorus determinations, by reducing with zinc, and titrating with permanganate.

The blank or dummy test is a highly important one. It must be done on a molybdenum-free steel in exactly the same way as the test the same amount of hydrochloric acid and the same amount of chromium. Both the hydrochloric acid and the chromium affect the dummy, the former very greatly, and the latter slightly.

Dummy test, without hydrochloric acid.
Dummy test, with hydrochloric acid..

Permanganate.

CC.

0.6

1.2

Below are results obtained by use of the latter dummy result (chromium not added) in steels containing same amount of chromium as molybdenum.

Although the most of the chromium is precipitated with the iron, it would seem from these results that enough passes into solution to slightly affect the end-point of titration. necessity for its presence in the dummy test.

Hence the

In the gravimetric method the first lead molybdate precipitate

is always contaminated with a little chromate.

LABORATORY OF HENRY DISSTON & SONS' STEEL WORKS,

PHILADELPHIA.

PRELIMINARY NOTE ON A NEW SEPARATION
OF THORIUM.

BY FLOYD J. METZGER.
Received January 6, 1908.

N an investigation still in progress, attention has been par

for the separation of thorium from cerium, lanthanum, and didymium, and it is in this field that it is desired to announce some preliminary results.

It is found that from a 40 per cent. alcoholic solution, thorium is precipitated quantitatively on the addition of fumaric acid, while no change is produced by that reagent in cold solutions of cerium, lanthanum, or didymium.

The experiments already made show that a good quantitative separation of thorium from these elements can be based upon this reaction. When thorium is precipitated in this manner in the presence of either cerium, lanthanum, or didymium, traces of the latter elements are carried down, but may be removed by a single reprecipitation. It is intended to compare this method with those at present in use for the analysis of monazite.

A number of other weak organic acids are being investigated along the same lines, and several of these show interesting results.

QUANTITATIVE CHEMICAL LABORATORY,

COLUMBIA UNIVERSITY.

NOTE.

Reinsch's Test for Arsenic.-To obtain a black deposit upon a piece of copper is a comparatively easy matter; to prove that this deposit is due to the presence of arsenic is perhaps more difficult. In place of the usual glass tube, Sheridan Delépine' recommends a "thimble-shaped copper cone" half an inch high, inserted through a hole in a thin iron plate, the sublimate of arsenious oxide being formed on a microscope cover glass. The following simplified form of the above arrangement I have found extremely convenient for the detection of very minute quantities of arsenic.

In the center of a piece of sheet copper an inch or so square, a small depression is punched, an eighth of an inch deep and of about the same diameter. The arsenic is deposited from solution on a little piece of copper a few millimeters in area. After being washed and dried, the little piece of blackened copper is placed in the depression in the sheet metal. A microscope cover glass, having a drop of water on its upper surface, is now placed over the miniature copper crucible, and the latter is then gently heated over a very small flame. When examined under a high power of the microscope, the crystals of arsenious oxide may sometimes be seen even when no sublimate is visible to the naked eye. Careful attention to the illumination is, of course, necessary. EDGAR B. KENRICK.

UNIVERSITY OF MANITOBA,

WINNIPEG.

1 Abstract in J. Soc. Chem. Ind., March, 1901.

NEW BOOKS.

ON THE COMPOSITION OF DUTCH BUTTER. BY DR. J. J. L. VAN RYN. London Ballière, Tindall and Co. 1902. 55 pp.

Samples of pure butter from Holland having been declared by English chemists to be mixtures of butter and margarine, the Netherlands government directed Dr. van Ryn to make an investigation of the variation in chemical composition of Dutch butters known to be genuine, in order to ascertain the cause of the abnormal composition.

In the first portion of his treatise, the author discusses the characteristics of pure butter, especially with reference to the percentage of volatile fatty acids as represented by the ReichertWollny number. He calls attention to the various factors influencing this number, such as advance of lactation, food, environment, etc., stating the views of various authorities.

The second portion of the paper gives the detailed results of his investigation. Samples of butter were obtained during the months of September, October, November, and December, from thirteen different herds, varying in size from 3 to 144 cows each, and from twelve different creameries. It was during the fall months that Dutch butters had been found abnormal. The author gives statements as to number, breed and age of cows, dates of calving, nature of soil, kind of food, and date of stabling. The tabulated analytical results are given under the heads of refraction, specific gravity, volatile acids (Reichert-Wollny), insoluble and soluble acids (Hehner), saponification number (Koettstorfer), and iodine number (Hübl).

The volatile acid number was found to be the best factor to use in studying changes of composition. The following statements indicate the most important results reached :

1. Of 428 samples of pure butter examined, just one-half fell below 25 in respect to the volatile acid number, this figure being the lowest limit accepted in England for pure butter. Nearly 10 per cent. of the samples were below 22.

2. The amount of volatile fatty acids began to decrease in September, and reached its lowest point in October, after which it rose gradually, as indicated by the following monthly averages: September, 24.8; October, 23.7; November, 25.2; December,