 |
|||
|
|
|||
| ||||||||||
|
|  MIL-E-70610(AR)
Transfer a 25 roil. aliquot from the volumetric flask to a 150
ml . erlemeyer flask with a standard taper joint. From a 10 ml. Mohr
pipet, add 8 ml. of freshly prepared 2N sodium hydroxide solution, a
strip of litmus paper (Note 3), and more sodium hydroxide solution,
dropwise, until the paper just turns blue. Wash the flask mouth and
walls with water. Add 1N hydrochloric acid, a drop at a time, until
the color of the litmus paper just reverts to red, and then one drop
more. Attach the flask to a water-cooled condenser, reflux for 15
minutes, then remove the flask and lace it in a cold water bath
(Note 4).
When cool, wash the contents of the flask into a 150 ml. beaker
and insert the electrodes of the pH meter (Note 5) . From the 10 ml.
buret add barium hydroxide solution (the volume need not be
recorded) in increments of about 1 ml. to pH 4, 0.5 ml. between pH 4
and pH 5, 0.25 ml. between pH 5 and pH 6, and 0.1 ml. between pH 6
and pH 6.7. When the pH exceeds 6.7, add only a drop at a time,
allowing 30 seconds between drops, until the pH is adjusted to 7.2.
Add 5 grams of mannitol and measure the volume of barium hydroxide
solution required to restore the Ph to 7.2, adding the solution in
progressively smaller increments in the manner already described.
Standardize the barium hydroxide solution not earlier than the day
before nor later than the day after that on which the titration was
performed.
To standardize the barium hydroxide solution, pipet 25 ml. of
"blank" solution and 10 ml. of standard boric acid solution into a
150 ml. erlemeyer flask with standard taper joint. Adjust the
acidity, reflux, and titrate in the manner described in the previous
paragraphs. Calculate the strength of the solution as follows:
Where:
= Volume of barium hydroxide solution required to titrate
the aliquot of boric acid, ml.
= Weight of boric acid in the aliquot of boric acid
solution, mg.
13
|
|
Privacy Statement - Press Release - Copyright Information. - Contact Us |
Click
here for thousands of PDF manuals