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who is also said to have expressed an unfavourable opinion of the sul- 

 phuric acid method, and quotes a number of literary references on the 

 solubility of the higher benzene homologues in sulphuric acid, according 

 to which the method in question is utterly useless for this purpose. 

 Marcusson next attacks several misconceptions by Herzfeld with regard 

 to the modified nitric acid process and the apparatus for applying this 

 method devised by Marcusson and Winterfeld. 



Herzfeld's rejoinder to the above statements *), contained in an article 

 of a polemical character, is that the solubility of xylene in sulphuric acid 

 of which Marcusson speaks is by no means always so great as alleged 

 by the latter. For instance, pure m-xylene, when mixed with 50°/o of a 

 turpentine oil which, taken by itself, had given a residue of 5°/ when 

 treated with sulphuric acid, left not less than 52°/o residue, or equal to 

 49,5 °/o allowing for the residue of the turpentine oil, that is to say, almost 

 the theoretical value. Out of four samples of commercial xylene, three 

 gave figures indicating a xylene-content of from 87 to 97°/o, and the 

 literary references cited by Marcusson are therefore not to be accepted 

 as trustworthy on their face-value, although, of course, xylenes may occur 

 which are not exclusively composed of benzene-hydrocarbons. 



Herzfeld gives several reasons against the improvement of the nitric 

 acid process attempted by Marcusson. One of these is that Marcusson's 

 assumption that the nitrated portions of the benzene which pass over into 

 the acid are aromatic nitro-compounds is only to a small extent accurate. 

 Another is that the density of these bodies assumed by Marcusson (1,15) 

 is arbitrary, and a third, that of some portions of the nitrated bodies, a 

 part passes over into the acid, while another is held in solution in the 

 benzene. Herzfeld regards a further investigation of Marcusson's method 

 as desirable, and shows from mixtures of turpentine oil with benzene and 

 with benzene-hydrocarbons of different kinds that the sulphuric acid method, 

 in contradistinction to the two nitric acid methods, gives on the whole 

 an approximately correct idea of the composition of the mixtures. 



Nicolardot and Clement 2 ), in a paper which is further dealt with 

 below, also speak unfavourably of the results of the sulphuric acid test. 

 They believe that this method frequently gives rise to the formation of 

 cymene and of other compounds which are volatile with steam, scarcely 

 at all affected by sulphuric acid and separable from petroleum distillates, 

 and that these compounds may lead to the erroneous assumption of 

 adulteration with "white spirit" and similar substances. On the other hand, 

 many oils which have really been sophisticated with such adulterants may 

 pass as pure under this test, because in it the characteristic odour of the 

 adulterant disappears. A handy means of attaining this object, it is said, 

 consists in merely boiling petroleum distillates with a little turpentine oil. 



a ) Chem. Ztg. 34 (1910), 885. 



2 ) Bull. Soc. chim. IV. 7 (1910), 173. 



