In their study of the behavior of aldehydes toward phenylhydrazine Fischer and Knoevenagel1 found that when acrolein is used the product is 1-phenylpyrazoline instead of the expected hydrazone. Much later Auwers and Müller2 studied this reaction further, and reached the conclusion that the pyrazoline in this and other instances is formed through the rearrangement of an unstable hydrazone and noted that in those cases where the latter can be isolated, treatment of it with hot acetic acid causes rearrangement. This view was supported by the work of Auwers and Voss3 who isolated the hydrazones of cinnamic aldehyde and benzal-
Assuming the atoms of phenyl isocyanate and of diazobenzene-imide to be arranged as indicated in the formulas, C6H6NCO and C6H5NNN, application of the octet theory leads to the conclusion that they are isosteric. They should, therefore, be very similar in their physical properties. Their densities, vapor pressures and viscosities have been measured at various temperatures, and this prediction confirmed. These results also confirm the straight-chain structure for triazo compounds.
Not too long after photography's grand debut in 1839, physician and inventor oliver Wendell holmes described the new technology as a "mirror with a memory." What might this phrase mean for the question of african americans and their relationship to the vicissitudes of photography and the vagaries of memory in particular? through readings of works of art and social activism that make use of lynching photographs, this essay considers ways in which photography has functioned as a technology of memory for african americans, what the essay calls critical black memory, and proffers a mode of historical interpretation that both plays upon and questions photography's documentary capacity.The essay makes two claims specifically. First, the mechanical reproduction of lynching by way of the photograph has been central to the recounting and reconstitution of black political cultures throughout the Jim crow and post-civil rights era. from the usage of lynching photography in pamphlets by early twentieth-century anti-lynching activists, to posters created by mid-century civil rights organizations, to their deployment in contemporary art and popular culture, this archive has been a constitutive element of black visuality more broadly. Second, african american engagements with photography as a "site of memory" suggest a mode of historical interpretation in which african americans simultaneously critique the "truth-claims" of photography while they mobilize the medium's documentary capacity to intervene in the classification and subjugation of black life.
The same products were obtained in another experiment in which 0.5 cc. of piperidine was used as a catalyst.Azobenzene and p-Thiocresol.-A solution of 18.2 g. (0.1 mole) of azobenzene and 37.2 g. (0.3 mole) of £-thiocresol in 200 cc. of xylene was refluxed for twenty-five hours. As in all other experiments, a trap2 was used to exclude air. The products obtained were 9.5 g. of aniline, 0.1 g. of benzidine (from a sulfuric acid treatment of the hydrazobenzene present), 5.5 g. of £-thiocresol and 90% of the di-p-tolyl disulfide which should have formed on the basis of the reduction products isolated.Miscellaneous.•-After heating 0.075 mole of benzophenone-anil with four molecular equivalents of ^-thiocresylmagnesium iodide in an ether-xylene solution at 103-107°f or twelve hours, 96% of the anil was recovered. In addition, 0.3 g. of aniline was isolated. Another experiment under corresponding conditions yielded a 95% recovery of the anil, and traces of aniline and di-p-tolyl disulfide.Subsequent to refluxing three equivalents of ^-thiocresylmagnesium iodide with benzalaniline in an ether-xylene solution at 114-124°for forty hours, 96% of the pthiocresol was recovered.The recovery of ^-thiocresol in an experiment in which four molecular equivalents of it were refluxed with benzophenone in xylene for twenty-six hours was 97.8%. A like recovery of ^-thiocresol was had in an experiment wherein eight equivalents were heated with nitrobenzene in xylene for twenty-six hours.
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