CHEMICAL NEWS, May 23, 1919

THE CHEMICAL

VOL. CXVIII., No. 3084.

NEWS

ON ACQUIRED RADIOACTIVITY.*

By Sir WILLIAM CROOKES, O.M, LL.D., D.Sc., &c. (Concluded from p. 231).

Action of Radium Emanation on Diamond and on other Bodies.

31. AFTER repeated observations on the action of radium on various substances, it was seen that diamond behaved differently to glass, quartz, and other materials, especially

if the action of the radium had been continued for some length of time. The following experiments were made to see if definite light could be thrown upon this point. Some plates and crystals of pure quartz, lead glass, Faraday's boro-silicate lead glass, and three diamonds were selected -well cleaned, and exposed upon a sensitive film for twenty-four hours. On development it was seen that all were inactive, except in the case of two of the diamonds, but from these the action was so slight as to be only just visible upon the film. These objects were now laid upon a table of clean platinum gauze and enclosed in an airtight glass vessel, together with an open bottle containing pure radium bromide. They were allowed to remain exposed to radium emanation (33) for forty-eight hours; they were then removed from the chamber and laid upon a sensitive film for twenty-four hours. Upon development each object was found to be active and there was nothing to show that the three diamonds had acted differently to the quartz or glass. The objects were now all boiled in dilute nitric acid and thoroughly washed in clean water. They were placed on a film and allowed again to remain for twenty-four hours; on development it was seen that practically the whole of the "activity" had been removed the two diamonds that originally were very slightly active had, perhaps, gained a little, but all the other objects had lost their temporary activity.

32. The experiments were still further extended. Two fragments of lead glass and one diamond crystal that had been buried in radium for over two years and had become deeply coloured, the diamond green and the lead glass

brown, were removed from the radium and cleaned as far as possible with a dry brush. They were kept upon a film for five days. On development the photograph showed three equally dense black patches. The glass and diamond were now boiled in dilute nitric acid, thoroughly washed, laid upon a film, and kept there for eighteen hours. Upon development the pieces of glass were seen to have almost lost their activity-the dian ond gave a dense black impression. The objects were now placed in a mixture of fuming nitric acid and potassium chlorate and kept just short of boiling-point for six hours, frequently removing the weakened solution and adding fresh acid and chlorate (3, 9, 12); they were then thoroughly cleaned, dried, and laid upon a film for eighteen hours. On development the glass blocks gave impressions slighly fainter than before, while the diamond still gave a dense black image almost as strong as before the treatment.

33. An examination with a zinc-sulphide screen showed

that the diamond caused brilliant scintillations from its edges and corners and a few erratic scintillations could be detected round each of the fragments of glass (11, 17, 26, 27, 30). The net result of these experiments is to show that, although the well-known condensation of emanation (31) upon crystals and objects gives rise to

A Paper read before the Royal Society. From the Philosophical Transactions of the Royal 9o. iety, ccxiv., A, 521.

241

photographic markings of patterns as described in this research and in previous papers by Sir Ernest Rutherford ("Distribution of the Intensity of the Radiation from Radioactive Sources," Phil. Mag., August, 1906) and other ebservers, this superficial activity can be easily and completely removed by washing in dilute acids. The diamond crystal that had been rendered active by immersion in dry radium bromide for some months in 1906 (17) and has been treated with acids, heated, and used in hundreds of experiments since-is apparently as active now as when it was removed from the radium, and still pours out streams of a-rays.

(These experiments are closely connected with those of Swinton, Colley, Ramsay, and others, who have shown that helium is driven into the glass walls of a vacuum tube even by the slower moving cathode rays. The high speed a-particles evidently are driven into the diamond, below the molecular surface).

the action of radium retains its colour and activity, and 34. As in the case of diamond, a quartz glass dish after continues to give off a-, B, and y rays. One-half had a film of aluminium, o'035 mm. thick, interposed fused silica that have been much used for the crystallisabetween the dish and the sensitive plate. Vessels of pure tion of radium salts become coloured a purplish tint, similar to that assumed by soda glass in similar circumstances. On heating such a coloured vessel with a spirit lamp to a temperature much below a red heat it suddenly phosphoresces a bluish colour and at a red heat becomes

colourless.

heavy glass (sp. gr. 3.87), polished on its three refracting 35. A small equilateral prism was cut from a block of faces, but lett rough ground on the triangular top and bottom. It was put into a bottle and covered with dry crystals of radium bromide for fifteen hours. At the end of this time it was removed, well washed, and placed on a sensitive film, base downwards, for twenty-two hours. flow radiation along the sides and the continuation of the On development a strong action was apparent with overfaces in triangular lines, as observed by Sir E. Rutherford.

36. One of the rough ground bases of the prism was now polished over the greater part of its surface, leaving condition. This end was then laid on a sensitive film for a strip of glass along one edge in its original unpolished thirty six hours. On the polished portion of the surface there was absolutely no perceptible action on developing, while the part left unpolished was highly active - as in the first experiment with the prism.

of its polished faces for twenty-four hours. On develop37 The prism was now laid on a sensitive film on one ment slight action was observed where the polished face touched the sensitive surface and a much stronger overflow action with continuation of the edges of the prism face in straight lines as mentioned above.

made with a writing diamond across the same face that 38. The same prism was taken, and a diagonal scratch touched the film in the last experiment. It was laid with this face downwards on a sensitive film for twenty-four before where the face touched the film, but the line of hours. On development the image showed action as scratch where the surface of the glass had been abraded by the diamond was blank, showing no action whatever.

39. A triangular plate, about 1 mm. thick, was polished on its three edges, and kept in a bottle of solid radium bromide for sixty-eight hours, then laid on a sensitive film for four hours. There was very little action to be seen on development on the part where the face touched the film, but there was strong action radiating from the edges, with a continuation of the line of edge from each point. The plate was now cut into two equal parts, and the two tive film and there kept for forty-eight hours. On dehalves, separated about a centimetre, were laid on a sensiveloping, it was seen that the action of the flat surface was the same as before, but while the overflow action from the original corners was also the same, there was no action at all along the cut surface.

40. A glass tube that had contained 25 mgrms. of radium bromide was cut in half to remove the radium, and well washed and boiled in acids. It was of a dark blue colour. After being in a cabinet for many months the two halves were laid on a sensitive film in a line, the cut surfaces opposite each other aud separated about 2 mm. After four hours' contact the film was developed, when the appearance presented that of a streaming brush discharge from the two ends of each half-the part where the tubes themselves rested having made no impression.

Superficial Action of Radium on Mica.

41. Radium bromide has been imported from the Continent in small ebonite boxes covered with a disc of mica. One of these discs was first well washed to remove any adhering grains of radium salt-it was then split into four flakes. The upper flake, of a strong brown colour, discharged the electroscope in three seconds. The next film, also showing brown discoloration, required 3'5 seconds. The third film, not discoloured at all, required twelve seconds, while the last film, which had been furthest from the radium, required eighteen seconds for discharge, showing that the greater part of the activity was near the surface and corresponded with the coloration.

Action of B-rays on Diamond.

These two diamonds were subjected to the action of solid radium bromide, and the intensity of the phosphorescence thereby induced was seen to be of the same character as that caused by the X-rays. An extension of the experiment with radium, described in the next paragraph, showed that the effect of phosphorescence was mostly due to the B-rays (10, 19, 26).

43. An apparatus (Fig. 1) was fitted so that the active rays from a bottle of radium bromide (A) should pass through a tube drilled through a lead block (B), and allowed to pass upwards on a diamond (c) supported on a plate of aluminium, o'02 mm. thick. This was arranged between the poles of a powerful electro-magnet, so that the active rays from the radium should pass through the bole and act on the diamond when the magnetism was off, and be deflected from it when the magnetism was on,

A screen of barium platinocyanide put over the hole in the lead block showed a circular spot of phosphorescence. This luminosity vanished when magnetism was turned on, and reappeared when it was turned off, showing that the luminosity on the screen was chiefly due to the B-rays (10, 79, 26). The two large and small diamonds used in the last experiment were put side by side on the aluminium, and the support so arranged that it could be moved sideways to put either stone over or away from the hole in the lead block. It was easy to see by small movements of the support that, as in the case of the X-rays, the large stone was much more phosphorescent than the smaller stone. There was considerable residual luminosity, each of the stones continuing to glow with its relative intensity when effectually removed from the radium. Having found the position of maximum brightness for the large stone when over the radium, the current was turned on, so as to deflect the B-rays. At once the glow declined, and the residual phosphorescence faded. On taking the current off, so as to allow the B-rays again to come into action, the brilliancy increased again. There was no doubt as to the action, although the undeflected y-rays and the residual luminosity tended to obscure the observations.

44. The results described in this paper may be summarised as follows :-Various objects, diamond, ruby, garnet, quartz, gold, platinum, &c., also the phosphorescent substances yttria, calcium sulphide, zinc blende, and barium platinocyanide, are bombarded in a high vacuum by cathode rays, and in no case can any permanent activity be recognised either by photographic or electrical means (1, 2, 3, 4, 5, 6, 7).

Exposure to radium emanation confers temporary radioactivity on all bodies that have been tried; apparently due to the condensation of the emanation on the surface. This transient activity can be completely removed by washing in dilute acids (31).

Many substances become coloured by direct exposure to radium, the colour depending on the substance. Diamonds take a full sage-green tint, the depth depending on the time of exposure to the radium (33).

In addition to change of colour diamond also becomes persistently radio-active, continuously giving off a-, 3-, and y-rays. The acquired colour and activity withstand the action of powerful chemical agents, and continue for years with apparently undiminished activity (12, 31, 32). Removing the surface by mechanical means removes both colour and radio-activity (13, 16, 35, 37, 41).

The appearance of an auto-radiograph made by placing an active diamond crystal on a sensitive photographic plate, and the visual examination of its "scintillation" luminosity, suggest that there is a special discharge of energy from the corners and points of the crystal (18, 21, 23, 27, 33).

THE ANALYSIS OF PRUNE KERNELS. By LUCIA FORDYCE and D. M. TORRANCE.

IN the work we use 50 grms. of kernels. These were crushed, placed in a 250 cc. flask, connected with an inverted condenser, and ether was added. They were heated on the water-bath for more than sixty hours, when all the oil was extracted. The ether was then removed by distillation.

To get rid of the last traces of ether the residue, mostly oil, was placed in an open beaker and heated on the waterbath for two or three hours. We obtained 21 grms., or 42 per cent of oil.

On cooling the oils two kinda were found to be present. They were placed in a freezing mixture, and at minus 5° one of them solidified. The other oil was drawn off by means of a pipette and each was weighed. The oil which solidified weighed 7'0122 grms., and had a specific

CHEMICAL NEWS.

May 23, 1918

gravity of o 9055, and the other which remained liquid | weighed 14 grms. and its specific gravity was 0.9119.

To ascertain if the oils were volatile 2 cc. were left standing in the open air for forty hours. There seemed to be no loss in weight.

The saponification equivalent was found by treating a portion of the oils with 30 cc. of normal caustic potash solution in absolute alcohol. This was heated on the water-bath for twenty hours with an inverted condenser, when saponification seemed to be complete. It was then titrated with normal hydrochloric acid.

The portion that solidified at minus 5° resembled palmnut oil, and had a saponification equivalent of 239.8. The saponification equivalent of palm-nut oil is 241 and its specific gravity is 0.9055.

The saponification equivalent of the liquid portion of the oil was found to be 207 4. It has the characteristics of cocoa-nut oil, whose saponification equivalent is 209 and its specific gravity is 0.874.

When 50 grms. of the kernels were treated with alcohol instead of ether a very small quantity of solid oil separated out, but the amount was too small to investigate further.

The kernels remaining after the ether extraction were dried in the air for ten hours, and then at a temperature of 100 for fifteen hours; the dried residue weighed 23 grms.

The Gunning method was employed for the estimation of nitrogen. We obtained 2'47 per cent of nitrogen from the original kernels and 2.21 per cent from the residue after the oil was removed.

We extracted the sugar with Maxwell's apparatus (CHEMICAL NEws, cxvii., 122), using water as the solvent. The kernels were boiled for 250 hours, when no further trace of sugar could be detected with Fehling's solution. We obtained 37'42 per cent of sugar. By treating a solution of the sugar with sodium acetate and phenyl bydrazine hydrochloride we could detect the presence of fructose and glucose, with a possible small amount of cane-sugar.

Cornell College, April 22, 1919.

243

such that it requires a 200 grm. balance to give satisfact tory results, and naturally this leads to slow weighings In spite of all these points the tower has steadily gained place, due to its increased functions over the wet towers.

The new absorbent, soda asbestos, eliminates almost every undesirable feature of any combination yet placed in the hands of the chemist for the determination of CO2 gravimetrically.

The absortent is sold in granular form about 8 to 10 mesh. It serves as its own drier, no pentoxide or calcium chloride being required. It will absorb nearly to per cent of its weight of carbon dioxide, and can be used while the gas is flowing from 250-300 cc. per minute. The containing tower has a relatively small area and weighs loaded about 100 grms.

The Midvale bulb modified according to Stetser and Norton is a very simple and inexpensive apparatus, designed particularly for use with soda asbestos. The Nesbitt bulb, designed originally for soda lime and pentoxide, serves as an ideal apparatus. This latter bulb

NOTES ON THE DETERMINATION OF CARBON IN STEEL.

By L. JOSLIN ROGERS (University of Toronto).

THE development of a new absorbent mixture for carbon dix de, soda asbestos, has so simplified the apparatus used in carbon determinations that it is quite evident that this material will soon replace all others for this type of work,

Until recently there were practically two types of bulbs, those using potassium hydroxide solution and those requiring soda lime. The great drawback to the first class of bulbs was the inability to permit a flow of gas at a rate sufficient to allow of rapid work required in present-day practice. The introduction of the Fleming tower made possible the seven minute carbon determination. This rapidity led to the application of this method to supplant the inaccurate colour carbon in the "snap test" on a beat of steel.

The Fleming tower, which has been for the past five years coming steadily forward on account of its marked superiority over the wet towers, has in its turn several features which require most careful attention in order to secure exact results. These are as follows:-The soda lime used must be of the proper fineness, and its moisture content must be about 15 per cent. This excess of moisture rapidly consumes the pentcxide in the top chamber, which will accordingly require frequent renewal. Again both the soda lime and the pentoxide must be carefully watched for fissures which will permit the gas to pass through without absorption. The weight of the bulb is

was rather a failure for the original purpose intende, since it had only a layer of asbestos between the pentoxide and soda iime, and the top portion of the latter rapidly dried out and became useless. However, this bulb leaves almost nothing to be desired further when used with soda asbestos. One slight turn of the single stopper as seen in the diagram shuts off the bulb entirely from the air. There are no rubber portions to catch foreign material as dust, &c., and the exposed glass area is relatively small. The stopper is large, permitting easy filling. The Nesbitt bulb is used with the gas flowing in at the top, and has therefore only a packing of glass-wool over the aperture at the bottom. Since soda asbestos is of coarse granular structure, there is no loss of fine particles and the tower never fissures. It is a very satisfactory material also for filling the drying arm in either a Johnson or Vanier bulb.

Another feature which makes the use of either the Fleming or soda asbestos bulb desirable is that both towers will permit of a flow of gas fast enough that a full factor weight of steel may be burned to a fusion withou altering the rate. This use of a full factor weight is very desirable from several standpoints. The weight in mgrms.