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TABLE IV. Giving the Number of cc. of Added Water per Litre of Milk Examined, corresponding to the Temperatures -0'550° to -0.351° C. ("Les Nouveaute's Chimiques pour 1905," p. 276, par Winter).

H

A

87.3

0'501

89.1

taining the freezing mixture stands. We use a porcelain beaker, D, 16 cm. high by 10 cm. wide, for a freezing vessel, and tie around it, for insulation, a roll of flannel to the thickness of about 1 inch.

A circular hole, E, centrally situated in the top of the stand, carries the milk tube, F. We use a flat-bottomed tube, 14 cm. deep and 3 cm. diameter, for holding the milk sample. We find it much easier to get agreeing results with this size of tube than with the longer round-bottomed tube recommended by Winter.

From the Proceedings of the Royal Society, Queensland, xxiv., 165.

The indiarubber cork has two perforations for carrying thermometer and stirring rod respectively.

The first thermometer we used was a Beckmann graduated in one-hundredths. The special thermometer devised by Winter for this work was subsequently obtained from Paris, but we found the Beckmann easier to read. For the last year a thermometer graduated in onehundredths, a degree covering 8.5 cm. of the stem, and specially made for us of normal glass by the V.F.L., has been used and gives splendid results. The trouble of having to occasionally readjust the mercury of the Beckmann has been avoided, while the true zero-point, which is determined afresh at least once every day on which the thermometer is used, has not varied more than o'02° C. A small telescope, H, is used for reading the thermometer. The telescope is mounted on the stand in the usual manner. The stirrer, K, is a brass rod 2 mm. in diameter, the spiral part being partly flattened out and armed with four small points of wire, to break up the ice formed in standardising. In practice, 50 cc. of each milk to be tested is put into a tube fitted with a cork, and the tubes are put into crushed ice and allowed to remain there (generally standing in the ice chest) until required. By this means the freezing of each sample is started close to o° C. While the samples are cooling the freezing mixture is prepared. The ice is conveniently prepared from the ice block by means of the usual ice plane. Alternate layers of ice and salt (3 : 1) are added until the porcelain beaker is filled. When about half-filled an empty "milk" tube is put into the middle of the beaker and the mixture packed around this tube. On removing the empty tube when the beaker is filled, there is no difficulty in inserting the tube containing the milk sample. After filling the beaker, the shelf is put in position on the rests and the beaker put on it. A tube containing a sample is then put through the hole in the top of the stand into the freezing mixture. The indiarubber cork is inserted, carrying the thermometer and the stirrer. The thermometer has been so adjusted that the bottom of the

thermometer is about 2 cm. from the bottom of the tube when the cork is in position.

The stirrer is now worked up and down continuously at the rate of from one to two complete movements per second, to prevent the formation of a solid block of frozen milk in the tube as the temperature falls. As a rule the mercury will rapidly fall to a point below the true freezingpoint of the milk (surfusion of the milk), and then rapidly rise and become almost stationary; the highest point of the rise after the fall will be found to be very close to the true freezing-point. When the tube has become partly filled with finely broken up frozen crystals-experience with the method soon enables one to judge of the correct proportion of crystals to have in the liquid-the porcelain beaker containing the freezing mixture is removed by withdrawing the shelf c and lowering the beaker and the hand put round the tube G, so that its warmth may cause a rise in temperature, the stirrer being worked very gently until there is a rise of about two-hundredths on the thermometer scale. The hand is now removed and the milk well stirred, so as to surround the thermometer bulb with crystals of frozen milk.

The stirring is stopped and the temperature observedthe mercury will slowly fall, and when it becomes stationary the reading is taken, but should not be taken as final unless it remains constant for at least two minutes.

The position on the thermometer scale of the freezingpoint of water is determined in exactly the same way as in the case of milk, distilled water being first placed in one of the tubes F, and cooled in a mixture of ice and water. Particular care, however, must be taken to break up the ice formed and to prevent the formation of a shell of ice round the sides and bottom of the tube. The fine ice should extend from the surface to the bottom of the thermometer bulb to ensure a good reading. It is much easier to determine the freezing point of milk than that of water, owing to the fact that "milk" crystals are easily kept small, while water always tends to freeze in one lump. The difference between the freezing-point of the distilled water and that of the milk on the thermometer gives the freezing-point of the milk.

For deducing the proportion of added water from the determined freezing-point Table IV., extended from Winter's, is used.

RADIUM.* (Continued from p. 266).

APPENDIX I.

Our Radium Resources.t

By CHARLES L. PARSONS, Chief of the Division of
Mineral Technology, Bureau of Mines.

THE "wonders of radium," both fact and fable," have been treated so extensively in the scientific and public press that it is not my intention nor is it at all necessary to repeat them here. Rather it is my wish to-day to present to a body of men interested in the development of American mining the present commercial situation as regards radium and its ores, and to point out, so far as I may, some of those future developments that already begin to be more or less distinctly visible.

A bulletin on the radium, uranium, and vanadium situation, by R. B. Moore, physical chemist in charge of the Denver office of the Bureau of Mines, and K. L. Kithil, mineral technologist of the Bureau, will appear within a few weeks and will contain much detail of interest to the mining industry. Last April an advance

* Report No. 214. presented to the House of Representatives, U.S.A., at the 63rd Congress.

+ Paper presented before the American Mining Congress, Phila

delphia, October 23, by permission of the Director of the U.S. Bureau of Mines. Reprinted from the ournal of Industrial and Engineering Chemistry, vol. v., No. 11, November, 1913.

statement, authorised by the Director, regarding this | bulletin, brought out particularly the fact that practically all of the carnotite ore mined in the world in 1912 was shipped abroad, and that this country was furnishing annually nearly three times as much radium from its Colorado carnotite deposits as all the rest of the world put together. It was further pointed out that this material has been bought by European buyers at a price entirely incommensurate with its radium value and that efforts should be made to keep at home both the radium itself and the profits of its manufacture; also that too much stress could not be laid upon the extensive waste of valuable radium ore thrown on the dumps of mines and prospects-much of it under such conditions that it could never be recovered.

The publication of this statement has already resulted in an increase of at least 33 per cent in the price of carnotite ore, and European buyers are awakening to the fact that they must pay to the American miner a price nearer the actual value of his ore. Also, a much lower grade of ore is now marketable, for whereas six months ago ore containing 2 per cent uranium oxide was the lowest grade accepted by European buyers, agents of these buyers are now asking for and actually purchasing ore containing no more than half this content of uranium. Furthermore, the operators are taking more care in separating their lowgrade ore from the gangue and in protecting it from wind and weather. Moreover, old dumps are being sold, and ore that a few months ago was thrown aside as valueless will be recovered from them.

In this paper I shall refer to other facts contained in this bulletin and shall mention some new developments having a direct bearing upon the American radium industry which have taken place since the manuscript was sent to the printer.

As is well known to all of you, the popular belief has been that the chief source of radium is the mineral pitch blende, especially that obtained from the mines now under the control of the Austrian Government at Joachimsthal, Bohemia, and pitchblende is the richest and most eagerly sought uranium radium ore. Outside of the ore in Austria, the only pitchblende deposits of any size are those in Gilpin County, Colorado, from which some 30 tons more or less have been procured since the mineral became valuable as a source of radium. The Denver❘ papers recently announced that these pitchblende-bearing mines have been acquired by Alfred I. duPont, of Wilmington, Delaware, and it is greatly to be hoped that their exploitation under his direction will yield an increased supply of this valuable mineral. It is not, however, so generally recognised that the mineral carnotite, which outside of the United States occurs only in low-grade ores mixed with ilmenite in the Olray district of South Australia and as a calcium carnotite (communicated by W. F. Hillebrand) under the name of Tyuyamyunite in Ferghana, Russian Turkestan, is by far the more important source of radium. From the most authentic sources it can be definitely stated that the Australian and Russian deposits do not compare in extent or richness with our own. The American carnotite is accordingly the largest source of radium at the present time, and at least four times as much radium was mined in America in the form of carnotite in 1912 as has been produced from Colorado pitchblende since it was first discovered in that State.

Valley, but they are nearer to the railroads and transportation costs are much less. The Green River deposits have apparently become regular producers. In Colorado, prospects have been opened at Coal Creek, 14 miles north of Meeker and at Skull Creek, 65 miles west of Meeker; but the richest of all American carnotite localities and indeed the richest known radium-bearing region in the world is that of the Paradox Valley, Colorado, extending from Hydraulic on the north to the McIntyre district on the south.

Geologists are now in the field making a special study of these carnotite ores with special reference to their occurrence and origin, of which altogether too little is now known. In the Paradox region the deposits seem to lie invariably just above the fine-grained La Plata sandstone. This rock is usually exposed high on the sides of the canyons, some of which are excelled in extent and in natural beauty by only the Grand Canyon itself. In a few instances, as at Long Park and Club Ranch, the deposits are only a few feet under the surface, the higher formations having been eroded; but for the main part, the stratum in which the carnotite occurs, when not entirely eroded, is deep below the surface of the mesa. Accordingly prospecting is mainly carried on along the sides of the canyons, and where vanadium and uranium stains are seen upon the rock the prospector blasts his tunnel in the hope of developing a pocket of the ore. The fact that the ore occurs in pockets renders prospecting uncertain, and there appears to be no present hope of insuring a successful search for pockets that are not exposed or do not happen to be near the surface. Although it is probable that many other pockets of carnotite occur at the same geologic horizon, their discovery, except where the ore-bearing stratum has been exposed by erosion, appears at present to be an almost hopeless task. The eroded sides of the canyons have been prospected again and again, but new claims are still being opened and are being sold by the prospector to the larger companies or operators who mine the ore. In such a sale the prospector and the purchaser both take a decided risk, for at present no method is used to determine the extent of the ore in the pocket other than the "prospector's hole."

As few of the prospectors of the west are acquainted with carnotite and pitchblende, the following description of the ores has been issued from the Denver office of the Bureau of Mines and is sent to all who make inquiry. "In reply to your letter for information concerning radium ores, the following facts may be of interest:"Radium is found associated with uranium minerals only. Wherever uranium exists, radium is also found in the mineral; and where there is no uranium, radium has never been found. Uranium and therefore radium are found in this country in carnotite and its associated minerals, and in pitchblende. Carnotite is a lemon-yellow mineral usually found in pockets in sandstone deposits. The mineral may be in the form of light yellow specks disseminated through the sandstone, or as yellow incrustations in the cracks of the sandstone, or may be more or less massive, associated with blue, black, or brown vanadium ores.

"Pitchblende is a hard, blue-black ore that looks something like magnetite, but is heavier. It is found in pockets and veins in igneous rocks. This mineral is not nearly as widely distributed as carnotite. Occasionally it is found associated with an orange mineral called gummite.

American carnotite is found chiefly in Montrose and San Miguel counties, Colorado, and in Utah north-west of these counties. The Utah deposits are at Green River, Table Mountain, Richardson, Fruita, Moab, and some sixteen miles south-east of Thompsons. The ores of these deposits are of a lower grade than those of the Paradox |

"The best way to test these ores is to wrap, in the dark, a photographic plate in two thicknesses of black paper. On the paper lay a key, and then, just above the whole in a light-tight box. Pressure of the ore on the key and plate should be avoided. After three or four days, develop the plate in the ordinary way; and if the ore is appreciably radio-active, an image of the key will be found on the plate.

"The U.S. Bureau of Mines, 502, Foster Building, Denver, Colorado, will be glad to receive any samples of