Di-nitro-benzol[A] | 16.67 | 16.78 |
| | | 16.57 |
| Para-nitro-phenol | 10.07 | 10.03 |
| Picric acid[A] | 18.34 | 18.42 |
| | | 18.43 |
| Ammonium picrate | 22.76 | 22.63 |
| | | 22.67 |
| Di-nitro-ortho-cresol | 14.14 | 14.10 |
| | | 13.98 |
| Tri-nitro-meta-cresol | 17.28 | 17.57 |
| | | 17.27 |
|_______________________|_____________|________|

[Footnote A: Dr. Bernard Dyer obtained 18.39 per cent. for picric acid and
16.54 per cent. for di-nitro-benzol.--_Jour. Chem. Soc._, Aug. 1895.]

When Chenel endeavoured to apply Jodlbauer's modification of Kjeldahl's
process to the examination of the tri- and tetra-nitrated naphthalenes, he
found that good results were not obtainable, because these compounds do
not dissolve completely in the cold sulphuric acid. It may, however, be
used if they are previously converted into the naphthylamines, according
to the plan proposed by D'Aguiar and Lautemann (_Bull. Soc. Chim._, vol.
iii., new series, p. 256). This is rapidly effected as follows:--Twelve
grms. of iodine are gradually added to a solution of 2 grms. of phosphorus
in about 15 or 20 c.c. of bisulphide of carbon, this solution being
contained in a flask of 250 c.c. capacity. The flask and its contents are
heated on the water bath at 100 deg. C. with constant attention, until the
last traces of the carbon bisulphide have distilled away. It is then
cooled, and the iodide of phosphorus is detached from the sides of the
flask by shaking, but not expelled. The next step is to add about 0.5 to
0.6 grm. of the substance that is to be analysed, after which 8 grms. of
water are introduced, and the flask is agitated gently two or three times.
As soon as the reaction becomes lively, the contents of the flask are well
shaken. It is usually finished about one minute after the addition of the
water. The flask is now cooled, and 25 c.c. of sulphuric acid, together
with 0.7 grm. of mercury, are gradually added; hydriodic acid (HI) forms,
and the temperature of the flask must be raised sufficiently to expel it.
The remaining part of the operation is as in the ordinary Kjeldahl
process.

M. Chenel has found this process the best for the analysis of the nitro-
naphthalenes, and for impervious substances l