A tall form 600 ml beaker was secured in a three jaw extension clamp attached to a vertical support rod and clamp holder and lowered into the center
of a clear plastic bowl of about 3 liters capacity sitting atop a magnetic stirrer . A stirbar was placed in the beaker , and a thermometer was held
in a thermometer clamp was lowered vertically until its tip nearly touched the bottom near the inner wall of the beaker where it would not interfere
with the spinning stirbar . The plastic bowl was filled about a third full with ice cubes and a fume intake and exhaust hose was held in a ring near
the opening of the beaker . To the beaker was added 100 ml of d 1.5 ( 97% ) pale yellow HNO3 which had been pre-measured in a 100 ml glass stoppered
volumetric flask and prechilled in a freezer to -10C . The stirrer was started at a low speed and 1 gram of urea nitrate was added . Additions in
small portions of 33 grams total pentaerythritol by sprinkles from a teaspoon were begun , observing the temperature and maintaining the reaction in
the range of 18-23C by regulating the rate of addition and adding ice to the bath as needed , siphoning off excess of melt water IIRC was at least
once required as it takes a surprising amount of ice for even this small batch nitration . It is a very exothermic nitration and should be carefully
watched . The total reaction time was 1 hour from the beginning of the addition to the completion of the nitration . The pentaerythritol appears to
first dissolve in the strong acid and then in seconds precipitates as the end product insoluble in the mixture as fine crystals which accumulate
steadily , making the mixture thicken more and more as the process continues until towards the end the slurry of PETN is so thick as to be barely
stirrable . The temperature range is critical , for at 25C red fumes will appear , but the reaction seems well behaved in the 18-23C range . At the
end of the hour the mixture is quickly drowned with ice water , plunging the beaker sideways into its own icewater bath is fine for this , and the
PETN filtered , suspended in warm water and neutralized with sodium bicarbonate and a little ammonia and then filtered and dried . The crude PETN was
placed in a sealed 1 liter jar with a magnetic stirbar and 375 ml acetone . The loosely capped jar was placed in a hot water bath on the stirrer and
heated just to the boiling point of the acetone , cooled slightly below and then unsealed . To the solution of PETN in acetone was added 1 gram of
urea and 1 gram of sodium bicarbonate and the mixture capped lightly and stirred for a couple of minutes and then 2 ml of strong ammonia water was
added . To the rapidly stirred hot acetone solution was then added in portions small pieces of ice allowing each portion to melt before more was added
, total ice about 200 grams , simultaneously with a slow drip 1 drop per second of warm water 250 ml containing about 1% urea as a stabilizer . When
all was added the stirrer was stopped and the mixture allowed to stand for a few minutes and filtered . The dried crystals of PETN weighed 73.6 grams
, yield 96% of theory based upon pentaerythritol used . The product is a snow white , colorless and odorless , reflective free flowing crystalline
material which very much resembles table sugar and is very temperature and storage stable , and has desirable handling and loading properties . The
product was dust free and appeared very consistent in particle size although it was not screened . It was good for use and lumpfree straight from the
drying on the filter , the sort of material where one simply folds the filter and pours the dried material directly into the storage bottle , and
there is little to no residue left sticking to the paper . Ah yes , the good stuff  |
