jarrod
April 24th, 2003, 11:07 AM
I have composed a guide for purifying nitric acid and am posting it for all to read and also comment on the procedure if you think there is a false statement or incorrect information, so please do share your opinion on my procedure.
Nitric acid purification
PURIFICATION
The nitric acid obtained at the end of my distillation is red to yellow-red. What this means is there is NOx present in our acid. NOx is not wanted so we need to extract it using an air pump, Teflon tubing and urea. The air used for bubbling needs to be dry, the air around us has too much moisture in it. To dry air is to desiccant air, for those that didn’t know that ;).
PREPARATION
· Obtain a tube that can be used for drying gases eg, U-tube (an improvised tube will do) and fill tube with the drying media. (Silica gel, Activated Clay (Montmorillonite) or others.) (http://www.s-cpp.com/pdf/Desiccant_Perf_Data-1.pdf)
· Get your pump and find the inlet hole/valve, (this is where it sucks the air in) put your thumb over the hole to completely cut off intake. Turn the pump on and see if air is still being pumped through. If so then take you pump apart and find where the air is being sucked in,(some pumps have more than one inlet.) To detect the air intake if it is not easily seen, blow smoke on the pump area and you should be able to see where the smoke is being sucked in. After these holes are found, block them leaving the one main inlet. (using glue, silicon or whatever it calls for.)
· Attach the drying tube to this hole/valve. Do not attach the glass directly! Use tubing, because this is how you will brake your glassware. Make sure there are NO leaks, reinforce your joints with “plumbers tape,” this is the white tape that is often around plumbing joints.
· Hook the Teflon tubing up to the tubing from the pump (using an improvised joiner eg: duck tape.) Again make sure there are NO leaks.
· To find leaks if not easily detected hold your thumb over the outlet (completely blocking the hole) and start your pump. Blow smoke over your joints an if a leak is present than the smoke will be blown away or sucked in to the tubeing.
PRODUCER
· NOTE that time frames are a guideline. If you notice an abnormality (using your judgment best as you can) stop, try again later and seek advice if it reoccurs continually.
· First fill a round bottom flask with your impure nitric acid (not to full to allow for error, 1/2 is sufficient) we do this because this because we don’t want any acid to spill on our skin or cloths, OUCH!
· After inserting the Teflon tube into the acid start bubbling dry air through it, (A constant stream of dry air, not so much as to cause the acid to foam up but enough to have lots of nice little streams of bubbles, youse your judgment.) You can slow the flow of air by slightly clamping the tube using a peg or something else.
· Ratio for urea addition is 1g urea to 100g acid (1% urea)
· For 100g acid add the urea over a time of 1 hour (0.1g every 10min) and continue bubbling for another 2 hours. If you just dump the urea in you will get urea nitrate and this is not wanted. (If you have twice the amount of acid, double the bubbling time, if three times then triple it, ect.)
· Swirl the flask (for a good minute) while adding the urea and then every now and again for the remainder of the bubbling.
· When bubbling is finished remove the tubing from the acid and while still inside the flask let any acid drip off.
· Our acid is now ready for use in other synthesises.
BUBBLER
· There are many ways to make a bubbler this is just one idea, just remember it all needs to be Teflon or resistant to the acid. Make a bubbler by blocking the end of the Teflon tubing and poking holes in it. Start by cutting two 10mm lengths of tube off the end.
Ž Cut down one side so it folds out and you have a rectangle of Teflon. Flatten this piece. (In a clamp, under some books ect…) after it is flat and will not curl, cut a circle out that has a diameter the same as the bore of your tube. (keep the scraps) DO THIS TWICE
Pic #1 (http://www.angelfire.com/pro/jarrod/images.html)
Ž Carefully insert the circles as to perfectly fit and block the tube (DO NOT glue, place it and leave it there)
Pic 2 (http://www.angelfire.com/pro/jarrod/images.html)
Ž Cut strip of Teflon from the scraps you saved. Poke a hole through the very end of the tube, now thread the strip through the holes. Thus blocking the most of the airflow, there will be air still coming out. (it should not be to much)
Pic #3 (http://www.angelfire.com/pro/jarrod/images.html)
Ž Now poke holes up the tube for the next 40mm (after the circles finish) and there is your bubbler.
· Test your bubbler in water and “tinker” until you have lots of nice little streams of bubbles coming from each of the holes you poked.
· Hook it all up so you’re ready to pump “Dry Air.”
So what do you think ?
Nitric acid purification
PURIFICATION
The nitric acid obtained at the end of my distillation is red to yellow-red. What this means is there is NOx present in our acid. NOx is not wanted so we need to extract it using an air pump, Teflon tubing and urea. The air used for bubbling needs to be dry, the air around us has too much moisture in it. To dry air is to desiccant air, for those that didn’t know that ;).
PREPARATION
· Obtain a tube that can be used for drying gases eg, U-tube (an improvised tube will do) and fill tube with the drying media. (Silica gel, Activated Clay (Montmorillonite) or others.) (http://www.s-cpp.com/pdf/Desiccant_Perf_Data-1.pdf)
· Get your pump and find the inlet hole/valve, (this is where it sucks the air in) put your thumb over the hole to completely cut off intake. Turn the pump on and see if air is still being pumped through. If so then take you pump apart and find where the air is being sucked in,(some pumps have more than one inlet.) To detect the air intake if it is not easily seen, blow smoke on the pump area and you should be able to see where the smoke is being sucked in. After these holes are found, block them leaving the one main inlet. (using glue, silicon or whatever it calls for.)
· Attach the drying tube to this hole/valve. Do not attach the glass directly! Use tubing, because this is how you will brake your glassware. Make sure there are NO leaks, reinforce your joints with “plumbers tape,” this is the white tape that is often around plumbing joints.
· Hook the Teflon tubing up to the tubing from the pump (using an improvised joiner eg: duck tape.) Again make sure there are NO leaks.
· To find leaks if not easily detected hold your thumb over the outlet (completely blocking the hole) and start your pump. Blow smoke over your joints an if a leak is present than the smoke will be blown away or sucked in to the tubeing.
PRODUCER
· NOTE that time frames are a guideline. If you notice an abnormality (using your judgment best as you can) stop, try again later and seek advice if it reoccurs continually.
· First fill a round bottom flask with your impure nitric acid (not to full to allow for error, 1/2 is sufficient) we do this because this because we don’t want any acid to spill on our skin or cloths, OUCH!
· After inserting the Teflon tube into the acid start bubbling dry air through it, (A constant stream of dry air, not so much as to cause the acid to foam up but enough to have lots of nice little streams of bubbles, youse your judgment.) You can slow the flow of air by slightly clamping the tube using a peg or something else.
· Ratio for urea addition is 1g urea to 100g acid (1% urea)
· For 100g acid add the urea over a time of 1 hour (0.1g every 10min) and continue bubbling for another 2 hours. If you just dump the urea in you will get urea nitrate and this is not wanted. (If you have twice the amount of acid, double the bubbling time, if three times then triple it, ect.)
· Swirl the flask (for a good minute) while adding the urea and then every now and again for the remainder of the bubbling.
· When bubbling is finished remove the tubing from the acid and while still inside the flask let any acid drip off.
· Our acid is now ready for use in other synthesises.
BUBBLER
· There are many ways to make a bubbler this is just one idea, just remember it all needs to be Teflon or resistant to the acid. Make a bubbler by blocking the end of the Teflon tubing and poking holes in it. Start by cutting two 10mm lengths of tube off the end.
Ž Cut down one side so it folds out and you have a rectangle of Teflon. Flatten this piece. (In a clamp, under some books ect…) after it is flat and will not curl, cut a circle out that has a diameter the same as the bore of your tube. (keep the scraps) DO THIS TWICE
Pic #1 (http://www.angelfire.com/pro/jarrod/images.html)
Ž Carefully insert the circles as to perfectly fit and block the tube (DO NOT glue, place it and leave it there)
Pic 2 (http://www.angelfire.com/pro/jarrod/images.html)
Ž Cut strip of Teflon from the scraps you saved. Poke a hole through the very end of the tube, now thread the strip through the holes. Thus blocking the most of the airflow, there will be air still coming out. (it should not be to much)
Pic #3 (http://www.angelfire.com/pro/jarrod/images.html)
Ž Now poke holes up the tube for the next 40mm (after the circles finish) and there is your bubbler.
· Test your bubbler in water and “tinker” until you have lots of nice little streams of bubbles coming from each of the holes you poked.
· Hook it all up so you’re ready to pump “Dry Air.”
So what do you think ?