400 



NATURE 



{Feb. 27, 1879 



the screw (s) left open to permit of the escape of the gas. As soon 

 as the whole mass of liquid has been reduced to a temperature of 

 - 23' the ebullition ceases, the screw (s) may be replaced, and if a 

 temperature lower than — 23° be required the tube (b) placed in 

 connection with a good air-pump. By this simple means a litre 

 of alcohol can be kept for several hours at temperatures either 

 of — 23° or — 55°, and thus a large number of experiments can 

 be performed for which hitherto the expensive liquid nitrous 

 oxide or solid carbonic acid was required. 



M. Camille Vincent has recently constnicted a much larger 

 and more perfect and continuous form of freezing-machine, in 

 which, by means of an air-pump and a forcing-pump, the chloride 

 of methyl is evaporated in the freezing-machine, and again con- 

 densed in the cylinders. This enlarged form of apparatus will 

 probably compete favourably with the ether- and sulphurous 

 acid freezing-machines now in use, as they can be simply con- 

 structed, and as the vapour and liquid employed does not attack 

 metal, is non-poisonous, and as the frigorific effects which it is 

 capable of producing are most energetic. 



The second and perhaps more important application of methyl- 

 chloride is to the manufacture of methylated colours. 



It is well known that rosaniline or aniline red, C2oH]9N3, 

 yields compounds possessing a fine blue violet or green colour, 

 when a portion of the hydrogen has been replaced by the radicals, 

 methyl or ethyl, and the larger the proportion of hydroi^en re- 

 placed, the deeper is the shade of violet produced. Then we 

 have triethyl rosaniline, or Hofmann's ^ violet, C2oHi8(C2H5)3N3. 

 By the replacing one or two atoms of the hydrogen of aniline 

 by methyl, and by oxidising the methyl-aniline, Charles Lauth 

 obtained fine violet colours, whilst about the same time Hof- 

 mann observed the production of a bright green colouring 

 matter now known as iodine green, formed during the manufac- 

 ture of the violet, and produced from this latter colour by the 

 action of methyl-iodide. 



In order to prepare aniline green from the pure chloride of 

 methyl a solution of methyl-aniline violet in methyl-alcohol is 

 placed in an iron digester, and the liquid rendered alkaline by 

 caustic soda. Having closed the digester, a given quantity of liquid 

 chloride of methyl is added by opening a tap, and the digester 

 thus charged is placed in a water bath, heated by a jet of steam 

 until the temperature reaches 95°, and the indicated pressure 

 amounts to from 4 to 5 atmospheres. As soon as the reaction is 

 complete the hot water is replaced by cold, and the internal 

 pressure reduced by opening the screw-tap of the digester. The 

 product of this reaction, heated and filtered, yields the soluble 

 and colourless base, whose salts are green. To the acidified 

 solution a zinc-salt is added to form a double salt, and the green 

 compound is then precipitated by the addition of common salt. 

 By adding ammonia to a solution of the methyl green salt, a 

 colourless liquid is obtained in which cloth mordanted with 

 tannic acid and tartar-emetic becomes dyed green (R. S. Dale). 



If rosaniline be substited for methyl-aniline in the preceding 

 reaction, Hofmann's violet is obtained. The application of 

 methyl- chloride to the preparation of violets and greens is, how- 

 ever, it must be remembered, not due to M. Vincent ; it has been 

 practised for some years by various aniline colour makers. M. 

 Vincent's merit is in establishing a cheap method by which per- 

 fectly pure chloride of methyl can be obtained, and thus render- 

 ing the processes of the manufacture of colours much more 

 certain than it has hitherto been. By the use of th's material the 

 aniline can be methylated in simple cast-iron boilers heated by 

 steam, and under a pressure much more moderate than is other- 

 wise required. 



In reviewing the new chemical industry of the beet-root'vinasses 

 one cannot help being struck by the knowledge and ability which 

 have been so successfully expended by M. Camille Vincent, on 

 the working out of the processes. Here again we have another 

 instance of the utilisation of waste chemical products and of the 

 preparation on a gigantic scale of compounds hitherto known 

 only as chemical rarities. All tho se interested in the progress 

 of scientific research must congratulate M. Camille Vincent on 

 this most successful issue of his labours. 



ILLUMINATION IN SPECTROSCOPY^ 

 A FTER having shown how intrinsic brilliancy of the light 

 ■^ operated on was the chief visual step to excellence in spec- 

 troscopic observations, the author proved that the temperature 

 ' Hofmann, Proc. Roy. Soc, xiii. 13 (1863). 



' Abstract of paper upon "' End on, in Place of Transverse, Illumination 

 in Private Spectroscopy, " by Mr. Piazzi Smyth, Past President of R. Sc. 

 Soc. Arts. Edinb., February 10, 1879. 



of the light must be kept constant, or we might be landed in a 

 totally different class of physical phenomena of a most con- 

 founding character. 



Coming, then, practically to ^awi?-spectroscopy, he described 

 the results hitherto obtained by all the leading spectroscopists 

 respecting the peculiar lines and bands, all of them very faint, 

 of the blue-grey blowpipe flame of coal-gas and common air ; 

 and then showed how, by merely looking at one and the same 

 flame end-on, in place of transversely, according to the nsual 

 custom, all the features hitherto chronicled may be seen some five 

 times brighter ; while many other details not dreamt of before 

 come into view, and the temperature remains undisturbed. 



Next applying the same principle to the electric-spark illu- 

 mination of gas-vacuum tubes, a still greater proportional 

 improvement was obtained. But not until the author had 

 invented or arranged a new description of such tubes, which 

 rendered the application of the end-on principle possible. Ex- 

 amples of these new tubes, as prepared lately for the author by 

 M. Salleron, 24, rue Pavee au Marais, Paris, were exhibited ; 

 and several proofs of their superior brightness of illumination 

 were given. The last being that in a narrow and critical region of 

 a rather faint and difficult carbonaceous spectrum, where the Royal 

 Society, London, has published eight lines only, and those 

 dark ones — the new tubes showed thirty-one lines, and all of 

 them bright ones. As yet the author had only been able to get 

 twelve different gases thus prepared ; but with such decided 

 improvement of spectroscopic vision in every case, that he hopes 

 so increased a demand may soon flow in upon M. Salleron, as 

 will make it worth his while to prepare similar end-on tubes of 

 all known volatile products ; and the result can hardly but prove 

 most favourable to the progress of spectroscopic science.^ 



UNIVERSITY AND EDUCATIONAL ' 

 INTELLIGENCE 



Dr. J, H. Balfour, Professor of Botany in the Edinburgh 

 University, has resigned his chair, which he has filled since 

 184S, on account of failing health. The patronage of the Chair 

 of Botany is vested in the curators of the University. Among 

 the candidates for the chair, we learn, are Mr. Carruthers, Prof. 

 Dickson, of Glasgow, Mr. J. Bailey Balfour, and Prof. 

 McNab, of Dublin. 



There was much fine talk last Wednesday at the Mansion 

 House on the subject of University extension in London, and it 

 was pleasing to see a prince take an apparently genuine interest 

 in the intellectual advancement of the people. We sincerely 

 hope that the movement may lead to a substantial and durable 

 result, though we very much doubt it. What we want most in 

 London is a true university after the German model, not a 

 " Cambridge extension." We are glad that Prince Leopold, in 

 his really able address at the Birkbeck Institution on Tuesday, 

 insisted so strongly on the weak point of the British work- 

 man, and that he can only hope to hold his own by the side of 

 the foreign workman by starting with an equally good education. 



At the annual meeting of the trustees of the Birmingham 

 Science College, under the presidency of the founder. Sir Josiah 

 Mason, who celebrated on Monday his eighty-fourth birthday, 

 it was announced that the college building, a handsome Gothic 

 structure in the rear of the Birmingham Town Hall, is rapidly 

 approaching completion, and the formal opening will probably 

 be made on the founder's next birthday. Nearly 150,000/. has 

 been expended on the college building and endowment. 



SCIENTIFIC SERIALS 



American Journal of Science and Arts, February. — We have 

 here two interesting papers on acoustics. Mr. Jacques has 

 inquired into the velocity of loud sounds, measuring the velocity 

 at different short distances from a cannon by means of a series of 

 membranes electrically connected with a chronograph. He finds 

 that the velocity of sound is a function of its intensity, and that 

 experiments in which a cannon is used contain an error, probably 

 due to the bodily motion of the air near the cannon. Immediately 

 in the rear of the cannon the velocity was less than at a distance, 

 but, going from the cannon, the velocity rose to a maximum 

 considerably above the ordinary velocity, and then fell gradually 

 to the rate usually received. When the cannon was pointed 



' Tubes similar to those referred to are already well-known in England ; 

 Dr. Monckhoven has in fact pointed out the value of such tubes, and sent 

 specimens to several observers in England. — Ed. 



