CHEMICAL NOTICES FROM NEWS SOURCES. Royal Society of Arts.-A Short Course of Four Lectures on " Heavy Oil Engines," by Captain H. Riall NOTE. All degrees of temperature are Centigrade unless otherwise Sankey, R.E. (ret.), M.Inst.C.E., will be given before the expressed. Comptes Rendus Hebdomadaires des Séances de l'Académie des Sciences. Vol. cliv., No. 8, February 19, 1912. Compounds of Neodymium.-Paul Joye and Charles Garnier. By spectroscopic methods the authors have discovered the existence of three different varieties of neodymium hydrate. When the hydrate is precipitated in the usual way it gives in reflected light a well-defined absorption spectrum. After it has been heated to 1000 it gives a reflection spectrum which has already been described as belonging to the oxide Nd2O3. The light reflected by the hydrate which has been heated to various temperatures between 300° and 700° gives two different spectra, quite unlike those of the hydrate and oxide. The author's experiments demonstrate the existence of a second hydrate, 2Ñd2O3.3H2O, formed from Nd203.6H2O by the loss of 3 molecules of water. s-Dioxy-thionaphthene.-Maurice Lanfry.-The author proposes to call those thiophenic molecules in which the oxygen is fixed to the sulphur s-oxy derivatives. He has prepared an s-dioxy-thionapthene by the action of hydrogen peroxide on thionaphthene in dilute boiling acetic solution. It does not possess the properties of the phenols, nor ketones, nor quinones. When treated with excess of bromine it gives a dibromide, C8H6SO2Br2. Apparently the fixation of oxygen by the sulphur of thiophenic hydrocarbons greatly facilitates the formation of bromine addition products. Fuming nitric acid instantly dissolves s-dioxythionaphthene, and from the solution crystals of the mononitro compound separate out. Action of Bromine in Presence of Aluminium Bromide on Methylcyclohexanols. -F. Bodroux and F. Taboury. The bromination of the three methylcyclohexanols by bromine in presence of aluminium bromide gives results analogous to those obtained with cyclohexanol. The action is energetic and yields a solid product and a yellowish oil. The former consists almost entirely of pentabromtoluene, while the oil is a mixture of several brominated derivatives. Berichte der Deutschen Chemischen Gesellschaft, Use of Magnesia Rods in Place of Platinum Wire. -E. Wedekind.-The author has found that little rods of magnesia about 1 mm. thick can be used instead of platinum wire in analytical work. The material is not pure magnesia, but the substance which is used for the supports of incandescent mantles. It is very resistant and can be used for flame tests and for borax beads. Small quantities of substances can be fused or volatilised on it, as on platinum foil. Dibenzyl and Diphenyl Silicols and Silicones.-Geoffrey Martin.-The author has prepared dibenzyl silicone, SiO(CH2.C6H5)2, by exposing a solution of dibenzyl silicol in caustic potash to the action of the carbon dioxide of the air for several days. Diphenyl silicol can be obtained by allowing diphenyl silicon chloride to drop into dilute ammonia or water. From it a diphenyl silicon can be prepared by heating to 140° and extracting with caustic potash solution containing methyl alcohol. Mirror-image Isomerism in Iron Compounds.-A. Werner. The tri-a-dipyridyl iron salts can be split into their mirror-image isomers by means of ammonium tartrate. The rotatory power of l-tri-a-dipyridyl iron tartrate is very great, but it very rapidly undergoes racemisation, probably because the salt gives up a-dipyridyl, and then remains in dynamic equilibrium with it. Royal Society of Arts, under the Howard Bequest, commencing on Monday evening, the 29th inst., at 8 p.m. Admission to the lectures is free to non-members of the Society on production of a Member's order, or by the personal introduction of a Member. The following is a syllabus of the lectures:— LECTURE I.—April 29.-The oil engine is an internal combustion engine-Difference between light and heavy oil engines-Difference between Diesel and other heavy oil engines-Brief history of the Diesel engine-Theoretical thermal efficiency-Heat and other losses-Actual thermal efficiency-Efficiency ratio-Thermal efficiency compared with other internal combustion engines and with external combustion engines-Cycle of operation of a 4-stroke and of a 2-stroke Diesel engine, and essential parts to produce these cycles. Considerations affecting design-Design of various parts, LECTURE II.-May 6.-Various types of Diesel engines shafts, frames, air compressors, &c., for 4-cycle and for such as cylinders, valves, pistons, connecting rods, crank2-cycle engines-Materials used for the various partsNumber and arrangement of cylinders for vertical and horizontal engines. LECTURE III.-May 13.-Description of Diesel engines manufactured by various makers-Sizes in current manu. facture and future possibilities-Speeds and weight for land and marine engines-Various kinds of oil available for Diesel engines; their characteristics, calorific value, and sources of supply. LECTURE IV.-May 20.-Economical results in respect of fuel and of total annual cost-Comparison of Diesel, gas, and steam engines, in respect of capital cost, fuel cost, and total annual cost-Various applications to land and marine purposes-Other heavy oil engines-Semi-Diesel engines. MONDAY, 29th.-Royal Society of Arts, 8. (Howard Lecture). "Heavy "Con Royal Institution, 5. Annual Meeting. THURSDAY, 2nd.-Royal Institution, 3. "Recent Explorations in the Canadian Rocky Mountains," by Prof. J. Norman Collie, F.R.S., &c. Royal Society. "Petrifications of the Earliest Chemical, 8.30. "Nor-hyoscyamine and Noratropine, Alkaloids occurring in various Solanaceous Plants," by F. H. Carr and W. C. Reynolds. "Researches on the Constitution of Physostigmine," by A. H. Salway. "The 'True Ionisation and Hydration Constants of Ammonia and some Amines, with a Note on the Formulation of Nitrogen Compounds," by T. S. Moore. FRIDAY, 3rd.-Royal Institution, 9. "The Use of Pedigrees," by W. C. Dampier Whetham, F.R.S. SATURDAY, 4th.-Royal Institution, 3. "The [Architecture of the Renaissance in France," by Reginald Blomfield. Supplement to CHEMICAL NEWS, May 3rd, 1912. DEVITRIFICATION OF SILICA GLASS.-SIR WILLIAM CROOKES, O.M., &c. I CHEMICAL NEWS, May 3, 1912 Devitrification of Silica Glass. 205 glass tube filled at once, only a microscopic bubble of air THE CHEMICAL NEWS. remained at the top. The silica tube, on the contrary, VOL. CV., No. 2736. ON THE DEVITRIFICATION OF SILICA GLASS.* By Sir WILLIAM CROOKES, O.M., For.Sec.R.S. THE use of apparatus blown and worked from melted quartz is now almost universal in chemical laboratories, especially where temperatures are required above the heat at which glass softens. When working at fairly high temperatures I was inconvenienced by the leakage of air through silica glass.† The apparatus (Fig. 1) was in the form of a perfectly clear and transparent tube, i cm. diameter and 20 cm. long, with a bulb 24 cm. diameter blown on the end. The other end of the silica tube was drawn out for connecting with the pump and sealing. It was exhausted to a high vacuum and heated to near redness along its whole length to remove any gas that might be condensed on the walls-it was then sealed off. only partially filled, and on measuring the mercury that entered it amounted to 10'15 cc., the capacity of the tube being 19 cc. Therefore in a few days air to the amount of 46 58 per cent of the total capacity of the apparatus had leaked in. A micro-photograph was taken of the surface of the devitrified silica bulb (Fig. 2). It showed a surface cracked all over into the appearance of cells. and on closer examination many of the cells showed decided hexagonal outline. I observed a similar appearance a few years ago when a silica dish, originally clear and transparent as glass, was used for evaporating down about 100 mgrms. of pure radium bromide. Patches appeared on the bottom having a dull roughened appearance, and on examination under the microscope the appearance was very similar to the surface of the devitrified silica bulb just described (Fig. 3). The appearances are so alike that it is legitimate to assume that the same cause had been at work, and that devitrification of the surface is produced both by exposure to a very high and long continued temperature and to the contact with a radium salt at a temperature of boiling water. I have not seen this effect on the surface of glass or silica bottles in which radium salts have been kept in the cold for some years. A NEW AND ACCURATE METHOD The tube was placed bulb uppermost in an electric resistance furnace in such a position that the bulb would be at the point of greatest heat, the lower part of the tube remaining comparatively cool; it was kept at a temperature of 1300° for twenty hours, at the end of which time the silica tube was removed from the furnace. The long continued high temperature caused the bulb and the upper FOR DETERMINING THE TRYPTIC Value of part of the tube to devitrify, and become white and translucent like frosted glass. The sealed-off end was carefully opened, and it was apparent that the inrush of air was by no means so strong as it would have been had the vacuum been as perfect as it was when the tube was sealed up. This looked as if there had been a considerable amount of leakage through the devitrified bulb, and I tried a test experiment. The tube was again attached to the Sprengel pump, and exhausted to as high a point as possible. During the progress of exhaustion, when the pump was rattling with the characteristic sound of a high vacuum, a large and powerful Bunsen flame was used to heat the bulb. Not the least difference in the sound could be distinguished. When the vacuum was at its highest the tube was sealed off, it was put into the electric furnace, and kept at a temperature of 1300° for eleven hours. After cooling the end of the tube was broken off under mercury. The mercury rose, but did not fill the bulb. The amount that entered was measured, and found to be 17.75 CC. Afterwards the tube and bulb were completely filled with mercury, the whole again measured, and the capacity of the tube and bulb was found to be 19 25 cc., showing that 15 cc. of gas, or 7.79 per cent of the tube's capacity, had leaked through the devitrified silica in eleven hours at 1300°. To ascertain if air would leak through the devitrified silica at the ordinary temperature a fac-simile of tube and bulb was made in glass, and the two tubes were simultaneously exhausted on the pump. They were both heated, allowed to cool, and sealed off at the same time. The silica and glass tubes were put in the balance case and kept there for some time. When they were both at uniform temperature the silica tube was weighed. The tube and weights not being moved in the meantime, weighings were taken hourly, the balance being untouched during the intervals. In eighteen hours the weight increased 0.048 grain. After the silica and glass tubes had been at rest for some days they were opened simultaneously under mercury. The *A Paper read before the Royal Society, March 7, 1912. Jaquerod and Perrot have shown that fused silica is permeable to helium and hydrogen at a low red heat. (Comptes Rendus, cxxxix., 789, Nov., 1904; and exliv., 135, Jan., 1907). PANCREATIN.* By CLARENCE F. RAMSAY, AT the present time very little attention is being paid to pancreation as regards its proteolytic activity. This is probably due to the fact that no satisfactory test has been proposed by which it might be ascertained just how much proteid a given sample of pancreatin will digest. The tryptic value of pancreatin should be taken into account, for it is more energetic than pepsin. In the case of pepsin considerable time is necessary for proteid to be converted into peptone, while trypsin converts proteids rapidly into proteoses and peptone. It has been stated that trypsin is so energetic that it will convert proteid beyond the stage of peptone into leucin, tyrosin, and other amides. The U.S.P. method for determining the tryptic power of pancreatin is very indefinite and uncertain because of the manner of testing the end reaction. It states that by adding a little nitric acid to a portion of the peptonised milk no coagulation should occur. As regards the word coagulation in this test there is a difference of opinion. If we are to think of coagulation as the result obtained when adding rennin to milk it would be better to call this separation a precipitation. The result depends altogether upon the amount of acid added. If a minute quantity of aeid is added, no precipitate is formed, while with more acid there is a decided precipitation. A large excess of acid generally results in solution of the precipitate. Acid will cause a precipitation in peptonised milk no matter how long the digestion takes place. In view of the importance of trypsin in pancreatin the writer wishes to propose a milk test which, if carried out exactly in accordance with directions, will give very accurate results. In testing the activity of enzymes, it is very important to adhere to certain conditions, such as temperature, time for digestion, &c. So it is in testing trypsin. This test determines the amount of pancreatin necessary to peptonise a given quantity of milk in fifteen minutes. The end reaction is determined by adding a slightly acidified solution of rennin to a portion of the peptonised milk and noting if precipitation or coagulation takes place. The final end-point of the test is reached when the milk is just sufficiently peptonised so that it will not be coagulated by the rennin. To determine this it is necessary to test the pancreatin first at wide ranges of strength, say, I to 700, I to 800, 1 to 900, &c. By this is meant I grm. of pancreatin to 700 cc. of milk. After it is found between what wide ranges the strength of the pan. creatin lies, a second series of tests are made at intermediate values until the exact strength of the pancreatin is found. In carrying out the test it was found necessary to make the milk slightly alkaline with sodium bicarbonate to prevent the pancreatin from curdling the milk. This coagulation is probably due to the presence of an enzyme in pancreatin similar to rennin. The materials required for the test are as follows:05 grm. pancreatin added to sufficient distilled water to make 50 cc. of solution. 900 cc. of milk containing 18 grms. of sodium bicar2 grms. bonate. of rennin (1: 30,000 in ten minutes or equiva. lent) and I cc. of 6 per cent acetic acid (U.S.P.) added to 50 cc. of distilled water. After warming the milk, place exactly 50 cc. in a cylindrical tube of about 100 cc. capacity. Prepare several such tubes and place in a water-bath, maintaining A NOTE ON THE ASSAY Of formaldehYDE.* the temperature at 40° C. Add to the tubes of milk the following amounts of the pancreatin solution : In each case note the exact time when the pancreatin is added, mix well, and after digesting fifteen minutes place 5 cc. of the digested milk in a test-tube, add 3 cc. of the rennin solution, and shake well. No precipitate indicates that the casein has all been peptonised, and that the pancreatin is stronger than the strength tested. For example, if there was no precipitation at 1: 700, but there was a precipitation at 1: 750, then it would be necessary to run more digestions between 1: 700 and 1: 750. fresh solution of pancreatin, and use the following By ELIAS ELVOVE. (Concluded from p. 202). Make a Amount of N/10 KCN added. (a) Cc. Amount of N/10 AgNO3 used. Cc. Cc. 25 33 31.50 25 25 40 48 12 2.30 32.23 2.38 32.32 (Temperature, 15° C.). In this manner it can be determined quite accurately how many times its own weight of milk a given sample of pancreatin will peptonise. In order to get accurate results the test must be carried out strictly in accordance with directions. As stated above acid will precipitate peptonised milk; therefore just enough acid is added to the rennin solution so that 3 cc. of this solution will neutralise the sodium bicarbonate in 5 cc. of the peptonised milk. Then the rennin will do its work, for it will not form the precipitate in an alkaline solution. "Attention must be called to the fact that pancreatin in a neutral solution deteriorates quite rapidly. Therefore this solution should be made up the last thing so that it can be added immediately to the milk. The amount of pancreatin solution suggested is sufficient for testing the strengths as indicated. It must be borne in mind that all tests of this nature are purely arbitrary; consequently a slight variation in the Carrying out of such a test would give different results. The method gives accurate results to within 2 or 3 per cent, which is closer than pepsin can be tested on egg albumen, and equal to the accuracy of the starch methods for testing diastases. If this proposed test is carried out 12 (a) 48 cc. of the KCN solution was equivalent to 47.56 cc. N/10 AgNO3 in Exps. 1-3; to 47.5 cc. N/10 AgNO3 in Exps. 4-12. These results, therefore, like the results given in Table II., show that when only a comparatively small excess of the KCN is used, the effect of a considerable variation in the temperature manifests itself quite markedly in the results, but when the excess of KCN is increased to about • The Chemical Engineer, xiv., No. 6. |