HCl gas generator

IndoleAmine · Dreamreader Deluxe

This is one good way of gassing liquids with HCl....

i_a

IndoleAmine · Dreamreader Deluxe

A few details I forgt to include: a bit of glasswool stuffed into the end of the condenser keeps the CaCl2 in place, and the gas dispersion tube is attached to the vacuum distillation takeoff with a piece of rubber tubing, so that if you would distill a liquid, it would be introduced into the receiver below the surface instead of dripping into the receiver from above... (hope u understand what I'm trying to explain here?)

And to prevent suckbacks, the dripping speed has to be adjusted properly so that a continuous flow of gas is produced; and in case it should still develop negative pressure by accident, simply lift off the stopper on the claisen for a second...

i_a

anime · Wed Apr 13, 2005 11:00 am

dont forget to add a stir bar to the reaction flask.. Bad things can happen if the HCl and H2SO4 do not mix...(esp when disposing the liquid...)

n00dle · Wed Apr 13, 2005 4:50 pm

he is not joking this nearly killed swim.
safety first

IndoleAmine · Dreamreader Deluxe

Right - of course the H2SO4 containing flask and heating bath have to be stirred all the time - else the result will be a sudden release of a huge giant HCl cloud instead of bubbling, and maybe even an explosion and spillage of hot, concentrated H2SO4... Shocked

(HCl 37% and H2SO499% can form two layers when stirring is insufficient; watch out and try to avoid it!)

i_a

bio · Working Bee

For those w/o an equalizing addition funnel something which works well is a large syringe (100ml+) with elastic over the plunger and under the grips which is tightened for drip rate adjustment. Refill as neededThis has 2 advantages: suck-back won't occur due to positive pressure and the temptation to walk away is less. Always a good idea to use a trap anyway

Even though a plastic equalizing add funnel is easy to make this gasser prefers the syringe for long procedures

IndoleAmine · Dreamreader Deluxe

A pressure equalizing pressure funnel for this application can be improvised by simply connecting the top of a simple addition funnel to the second inlet of the claisen (where the thermometer normally goes in) with two single-holed stoppers, glass tubing and a small piece of rubber hose.

(but then you have no stopper to lift in case of suckbacks, and will have to use a trap..)

i_a

bio · Working Bee

Must admit a few suckbacks have occurred and of course when a trap was omitted due to laziness. One of these destroyed a crystalline product due to sulfuric acid in the dryer ending up in the gassing mixture. Never again will a trap be left out. I just think of all the weeks of work leading up to the final step and all ruined, f.....k., then carefully assemble the acid trap.

IndoleAmine, I just had to laugh when I read your stopper lifting technique, which no doubt works. You must have the fastest stopper finger in the West is all I can say. Seems any suck back that ever happened to me was over in an instant. Do you use 1inch tubing or something? Very Happy

...........but then you have no stopper to lift in case of suckbacks, and will have to use a trap..........

IndoleAmine · Dreamreader Deluxe

Well - always alert and watching out for suckbacks to occur.... Very Happy

(after I found out that H2SO4 from a bubbler is a bad aldol condensation catalyst, I use just an empty flask as receiver, and the bubbler goes into a separate vessel conncected to the security trap with, guess what - 5mm silicone tubing... Laughing

)

Its not THAT bad if you watch for a steadily climbing bath temp. and adjust the dripping speed to faster from time to time, so you can be sure to have a positive gas pressure all the time.. Wink

IngInzano · Thu May 26, 2005 11:14 pm

HCl(aqu) + H2SO4= HCl(gas) ?????

IndoleAmine · Dreamreader Deluxe

Exactly.

The H2SO4 can dehydrate things, and can also dehydrate the HCl (which is a gas dissolved in H2O, so its a solution).

When the HCl has no solvent available anymore, it becomes clouds of HCl(g)..

Another option with this setup is to drip H2SO4 99% onto solid NaCl, but this is not as exact as using liquid HCl dripped into H2SO4 99%....

H2SO4 + 2 NaCl -> Na2SO4 + 2 HCl (and no H2O involved at all! Wink

)

joe_aldehyde · huxleys associate

it is even better to drip h2so4 cc. on a stirred mixture of HCl cc. and NaCl (s) but anybody who has a basic understanding of acid/base reactions knows what i am talking about.

mk-1 · Thu May 26, 2005 11:37 pm

I kinda like the washer bottle idea brought up in the hive by some1 (cant remember who, sorry).
U take a lab washer bottle (the one u fill with dH2O to wash stuff), load it with some NaCl, and wet the salt slightly with concetrated HCl. then u add concetrated H2SO4 and quickly close the tap. when u push on the bottle, it releases quite dry HCl gas.
useful for small batches.

hahas · Fri May 27, 2005 12:21 am

the use of liquid HCl is unnecessary - salt and 85% H2SO4 works fine for me.

joe_aldehyde · huxleys associate

this is true hahas, but you don't initially have to saturate your salt solution with HCl generated by h2so4...it's more like a cosmetical thing Smile