From: Yaritza Brinker <YBrinker**At_Symbol_Here**FELE.COM>
Subject: Re: [DCHAS-L] nitric acid distillation
Date: Thu, 15 Oct 2020 17:10:03 +0000
Reply-To: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**Princeton.EDU>
Message-ID: DM6PR05MB705287973A9AFF81F88694ABAD020**At_Symbol_Here**



As you mentioned, this is a very good opportunity for education. I encourage you to use this opportunity to develop a short seminar series on hazard assessment and good experiment planning practices for your students. Small companies will expect them to know who to do this on their own at the bachelor level.


Rather than calling out this particular case, you could use an experiment that is already being performed in the university as a case study or possibly an experiment that had been previously declined because it didn't pass hazard analysis. You could even tie it back to the course work by doing theoretical calculations related to the safety of the experiment.


Take a cyanide titration for example. You could calculate the amount of cyanide gas released if the pH were to drop during the titration. The lethal respirable dose is available. You can use this information to determine the scale of the experiment. You could even use your local ER response time to have the students think about the risk to human life if the experiment were to go seriously wrong.


Good Luck!


Yaritza Brinker



From: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**Princeton.EDU> On Behalf Of Laurie Yoder
Sent: Wednesday, October 14, 2020 10:12 AM
To: DCHAS-L**At_Symbol_Here**Princeton.EDU
Subject: [DCHAS-L] nitric acid distillation


** External Email **

We have a senior chem student who has proposed making fuming nitric acid by reaction of fertilizer and concentrated sulfuric acid. (wants to make rocket fuel because this is what they do on youtube...) After my first "no way on earth are you going to do this!" they looked up some safety information and sent me the "proposal", copied below. This is a highly motivated student who loves chemistry and legitimately wants to learn and try new things so I hate to shut them down without taking the opportunity for education. My problem is that everything about this looks high-risk, and I need some help to sort it out to best communicate what the concerns are, other than "you're going to injure yourself and damage the property."


My question for the group is what do you see as the top risks here and what would someone (in theory) need to do to mitigate them? I'm thinking (hoping!) it should become obvious to the student why we can't manage it here.


Thanks for your help!



This is from the student:

"I propose to produce fuming nitric acid using distillation of an alkali nitrate salt heated with concentrated sulfuric acid. Sodium Nitrate melts at 308 C and is an oxidizer which begins to break down but does not have a flash point. The high concentration Sulfuric Acid
will have some water in it but the Nitric acid being continuously produced boiling off should keep the temperature below 100 C anyway.
The temperature will be continuously monitored and the heater will be shut off if the temperature exceeds 150 C. 

"The reaction vessel will be a round bottom flask with a heater from there the gaseous nitric acid will run through a still cooled with ice water and covered with aluminum foil to minimize the breakdown of nitric acid into NO2 due to UV light. The product will be collected in another round bottom flask and the excess NO2 and uncondensed Nitric acid will be bubbled through a water trap (we shouldn't use rubber tubing here). 

"Products- Sodium Sulphate is a common fertilizer just like sodium nitrate the last of the acid in the reaction chamber can be neutralized and the waste can be easily disposed of as solid waste or mixed into the compost pile. 

"Fuming Nitric Acid- This is the product we are interested in collecting. It will be used by XXX as the oxidizing agent in a model rocket. Fuming Nitric acid quickly destroys Nitrile gloves, setting them alight and melting them. For this reason an alternative is necessary. Vinyl gloves deform a bit but do not melt or burn on contact with Fuming Nitric acid. Therefore obtaining Vinyl gloves and a Vinyl smock could also be a productive option. That said, direct skin contact with fuming Nitric acid is not as damaging to the skin as solutions containing more water. As long as it is promptly removed working without gloves would potentially be a viable option. All work will take place in the hood because gaseous nitric acid and NO2 are continuously released. Once the Fuming Nitric Acid is isolated it can be stored indefinitely in an amber glass container with a teflon sealed lid.

"Nitric acid from water trap- This product's density can be measured to determine its concentration. Then it can be stored in glass for use in other experiments.

"NO2 gas- We will do our best to minimize the production of this side product. Nitric acid breaks down into NO2 faster at high temperature and with more light. We will minimize the necessary temperature in the reaction pot, and ice the condensing regions and product. All the glassware connections will be greased using the same sulfuric acid in the reaction pot which would be a good reason to wear vinyl gloves. This will seal the reaction  with the overpressure continuously bubbling into the trap where more of the gas can condense and the extra NO2 will be pumped out of the hood where the entire synthesis will occur.

"Additional considerations
Limiting personnel access- Because the Chemical prep room is the only hood which is off limits to most students during the day it would be the ideal location for this synthesis. 2 people will monitor the reaction at all times and eyewashes and a shower are readily available. There is a designated fire extinguisher on hand and the labspace is not used too much so it can be cleaned up and sorted to meet our needs.
Eye protection- Eye protection will be worn at all times

"YouTube Sources

"Duke OESO Guidelines for Safe Use of
NITRIC ACID...[lots more copied and pasted stuff from internet...]


Laurie M. Yoder, PhD
Assistant Professor of Chemistry and Chemical Hygiene OfficerEastern Mennonite University


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