A new method for the analysis of commercial phenols / by S.B. Schryver.

  • Schryver, S. B. (Samuel Barnett), 1869-1929
Date:
[1899 or 1900]
Catalogue details

Licence: Public Domain Mark

Credit: A new method for the analysis of commercial phenols / by S.B. Schryver. Source: Wellcome Collection.

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    normal sulphuric acid are then introduced into the ammonia absorption bottle (C), and the phenol dissolved in about six times its weight of benzene is introduced into the separating funnel. This is then allowed to drop slowly into the sodium amide and benzene mixture, which is kept the whole time in a state of constant ebullition, and connected with the aspirator or water-pump. As soon as the phenol has been all added, the funnel is washed with a little more benzene, and air is aspirated through the apparatus until no more ammonia remains unabsorbed. The benzene holds the ammonia somewhat pertinaciously, and 1|- hour is generally required before the former is entirely driven out. Enough phenol is generally employed to require from 10—17 c.c. normal sulphuric acid for complete neutralisation of the ammonia evolved. At the end of the operation the excess of sulphuric acid is estimated by titration with normal sodium carbonate, methyl orange being generally used as Quantity of substance taken. Substance. h2so4 required for neutrali¬ sation of nh3 evolved. Quantity of substance found. Error. Grin. 1-05 Phenol (pure) C.c. 11*2 Grm. 1*05 0*00 1*03 99 10*7 1*05 + 0*02 1-03 99 11*0 1*03 0*00 1-03 99 10*7 1*00 - 0*03 1-61 Cresol (ortho) 15*1 1*63 + 0*02 2*08 Thymol 13*9 2*08 0*00 2-08 99 14*0 2*10 + 0*02 2’09 99 13*7 2*05 - 0*04 2’09 J' 13*6 2*04 - 0*05 2 ’09 99 13*7 2*05 - 0*04 2’09 14*0 2*10 + 0*01 2*05 Guaiacol (cryst.) ]6*4 2*03 - 0*02 2*06 99 16*6 2*06 0*00 2*06 99 16*6 2*06 0*00 2*06 99 16*5 2*05 - 0*01 2*06 99 16*4 2*03 - 0*02 indicator. In this way the total amount of ammonia evolved is readily estimated. The error in the titration should not deviate more than T^- c.c. from the theoretical amount required. In order to obtain accurate results, the following special precautions must be observed :— (i.) Both the phenol and the apparatus should be per¬ fectly free from moisture, as water acts on sodium amide (see above). The methods of freeing the phenol from moisture will be discussed in detail below.