M\K(il. I'M 2. 



KNO\VLi:i)(~.I' 



Phosphorus pentasulphide may be used in 



place of the trisulphide, in which case thiotenol 



CH'' — CH is obtained instead of thiotolene. 



CH:,-C 



C.OH 



The thiotolene or thiotenol is con\erted into 

 iso|)rene by reduction with liydrogen, effected b\- 

 passins,' a mixture ol citlur compound with 

 lu'drof^en over finely-di\'idcd copper or iron at a 

 temperature of 300°-50{l". 



CH--CH CH., 



CH,,-C 



2H, = CH.-C 



+ H.,S 



CH-CH, 



The ring breaks at the point indicated, the sulphur 

 lirst combines with the metal, and the resulting 

 sulphide is then reduced by the hydrogen, giving 

 sulphuretted hxdrogen, the above ecpiation showing 

 the final state of affairs. Aljove 50()~(" the iso[5rene 

 is con\-erted into dipentene. 



Drs. W. H. Perkin and C. \\"ei/maim ha\e 

 patented ' a process for iirejjaring isoprcne from 



amyl alcohol. Two parts of the latter are allowed 

 to stand with one part of zinc chloride for twent\'- 

 four hours and then distilled. This process 

 eliminates the elements of water from the amyl 

 alcohol, and the resulting amylene is converted into 

 isoprene by passing through a heated tube. Thus : — 



C,,H„. OH - H,0 = C.-,H,o = C,-,H, + H-, 

 .\iiiyl ;ilc()h()l. Amylone. Isopreiic. 



.V good deal of work is still being expended on the 

 problem of the inexpensive production of caoutchouc 

 by artificial means, and further results may soon be 

 expected. As to whether the synthetic article will 

 ever prove a dangerous rival to natural rubber it is 

 not possible to say.t Doubtless, in course of time, 

 increasing numbers of natural products will be 

 replaced b}- substances identical in all their properties 

 but chemically prepared ; — doubtless, also, sj'nthetic 

 caoutchouc (which at present is in its merest infancy) 

 has a future before it and will one day play a 

 part in hel[)ing to meet the alread\- enormous and 

 rajiidly increasing demand for india-rubber, lint 

 there is no cause for fear of aiU' decay in tlu' 

 rubber-growing industr\' on this ;iccount. 



' U. S. Patent. No. 991,453. W. H. I'crkin and C. Weizmann, Process of Manufacttirin^ Isoprcne. 



In Ibis connexion we must bear in mind that it is not without the region of possibiHty that natural rubber may owe some of 



its vahiable properties to the intimate mixture with the caoutchouc of the small quantity of other substances present. Tests to 



settle this <|Ucstion and to determine whether the synthetic, chemically-pure caoutchouc (as obtainable at present) is really 



physically identical in all respects with the natural article, do not appear to have been carried out. 



SOLAR I)lSTrRF,.\\XES DURING JANU.ARY, 1Q12. 

 I'.v FRANK C. DENNETT. 



.Adverse weather has much hindered Solar study during the 

 past month. At the same time the Sun has preserved a con- 

 dition of almost unruffled quietude to the telescopic observer. 

 Only on one day. January 5th, some faculic flecks showed near 

 the limb in the south-eastern quadrant, and so not far from 

 longitude 25° to 35°. They looked like the renmants of an out- 

 break. As the exact position was not measured it is impossible 

 to present the usual diagram this month. 



The progress of the cycle of solar phenomena is best shown 

 by the table of observations during the past eleven years. It 

 gives the number of days on which the Sun was observed, also 

 the number when spots were seen or taeniae only, and those 

 when there has appeared to be a clear disc. 



The consideration of these figures lead to the expectation 

 that the time of minimum will occur at the end of the present 

 year or early in 1913. The decrease of activity was earliest 

 noted in the northern hemisphere, and therefore the earliest 

 return may naturally be expected there. 



The eclipses of the Sun on April 17th and October 10th. 

 should be of special interest, as, occurring at a time of 

 minimum, the corona may be expected to present what is 

 known as a winged appearance. The poles of the Sun are 

 marked by short sharp plumed rays, whilst the coronal matter 

 is extended into elongated streamers in the equatorial regions. 

 It would appear probable the winged circles which figure so 

 largely in Egyptian temples, and so on, were designed from 

 such a phenomenon. The corona usually seen at the time of 

 maxinunn,asin 1905, is quite different, the polar plumes being 

 absent, and the coronal rays appearing to radiate in all 

 directions instead of being confined to the etjuatorial regions. 



Another feature noticeable at the time of mininunn is that 

 the prominences are fewer in number, and many forms which 

 are of frequent occurrence in times of activity are almost if 

 not entirely absent. Helium may always be observed in the 

 chromosphere as a bright orange line known as Dh. Frequently 

 it may al.'io be observed as a dark line amid spot groups, and 

 over faculae. During 1909, 1910, and 191 1 the observers who 

 co-operate in producing this monthly report have recorded the 

 presence of this dark Hue on 112, 85 and ii times respectively, 

 decreasing with the decrease of activity. 



The observers who contributed the material for the present 

 page were Messrs. J. McHarg, A. A. Buss, E. E. Peacock, 

 \V. H. Izzard, and the writer, at widely scattered stations, yet 

 they only succeeded in seeing the Sun on twenty-one days 

 throughout the entire month. 



Errata.— In the February number, page 59 in the 5th and 

 3rd lines from the bottom read 28° instead of 38°. 



