Subject: Re: Schoniger flask - purpose? From: dwilkins**At_Symbol_Here**orion.polaristel.ne t (Don Wilkins) Date: Sep 08 1996 Newsgroups: sci.chem.analytical On 7 Sep 1996 09:42:11 -0400, johnp99978**At_Symbol_Here**aol.com (JohnP99978) wrote: > I am reviewing a method to determine inorganic ions. This particular >method recommended the use of a Schoniger flask for sample preparation >(ashing). > > Could someone describe this type of flask? What is its purpose? Are >there any recent articles or references for this flask for further >reading? What is CONTRAD 70 solution? Never heard of Contrad 70 solution but then Alzheimers does take its toll. The Schoeniger flask is named for the developer of the procedure: Professor Wolfgang Schoeniger, a very competent microanalyst. The original was nothing but an Erlenmeyer flask and it was used for determining elements in organic compounds. Specifically chlorine but also adapted for other elements. Apparatus: 1. One Erlenmeyer flask (actually more than one because they exploded rather frequently) 2. One (one hole) rubber stopper for the flask. (Reusable after the flask explosions) 3. One glass rod with a platinum coil at the end stuck through the one hole rubber stopper so that when the stopper was inserted into the flask the Pt coil was a couple centimeters above the bottom. (Usually reusable after explosions) 4. Supply of oxygen gas. That answered all of your questions except for references but I suppose you would like to know how to risk life and limb with that collection of stuff. Procedure: 1. Add a few ml of dilute NaOH to a clean flask. 2. Weigh a few milligrams of sample onto a small piece of ashless filter paper. (Use the good stuff that has a low blank but determine what the blank is.) If you weigh too large a sample then be certain that extra flasks are available. 3. Fold the filter paper around the sample and place the folded paper in the Pt coil. 4. Fill the flask with oxygen. These next steps should be done rapidly with no hesitation between steps. You might want to make a few practice runs before wasting a sample. 5. Ignite the folded paper, insert the flaming paper into the flask, secure the stopper by pressing firmly, invert the flask so the solution forms a seal, shield eyes with other hand and grit your teeth. 6. If everything goes right you will get a clean burn and a bit of white ash will slowly drift down. 7. Shake flask for a few minutes to absorb chloride e.g. and proceed with analysis. Sometimes things don't go as planned. So if: A. Black unburned material is present go back to step one. B. Flask explodes. 1. Dry off and go back to step one. 2. Remove shards of glass, dry off, and go back to step one. 3. Remove shards of glass, dry off, explain procedure to technician and leave room during analysis. The analysis was first done on the lab bench with no concern for safety as described and I have seen Professor Schoeniger analyze a sample in a lecture hall. At that time some safety barriers were used but the explosion will leave a ringing sensation in your ears for a long time. As people pushed the sample size it became apparent that some precautions were in order. The laboratory supply houses saw an opportunity for earning a dollar and the apparatus became available commercially complete with safety shields, mechanism for inverting the flask, and would you believe remote ignition of the sample after ignition. Isn't progress wonderful? Now for you young'uns that procedure for analyzing organic compounds for chloride might not be a big deal but you should keep in mind that this simple procedure replaced combustion procedure using a Parr Bomb* containing several grams of sodium peroxide. Professor Schoeniger would complete a chloride analysis in a few minutes in a lecture hall but in the lab the analysis required several hours of work. It was sensational. Professor Schoeniger was a skilled and resourceful analytical chemist. The references will be found starting about 1953-4 and continue for a few years. You probably will find most in Z. anal. Chemie as he was either Swiss or German. Unfortunately he met an untimely early death and the analytical community lost a skilled researcher. ---------- *I never could understand why the Parr company used the word <bomb> instead of <pressure vessel>.
Newsgroups: sci.chem.analytical From: B.Hamilton**At_Symbol_Here**irl.cri.nz (Bruce Hamilton) Subject: Re: Schoniger flask - purpose? Date: Tue, 10 Sep 1996 18:17:13 LOCAL In article <323ac524.6256177**At_Symbol_Here**news .polaristel.net> dwilkins**At_Symbol_Here**orion.polaristel.ne t (Don Wilkins) writes: >On 7 Sep 1996 09:42:11 -0400, johnp99978**At_Symbol_Here**aol.com (JohnP99978) wrote: >> I am reviewing a method to determine inorganic ions. This particular >>method recommended the use of a Schoniger flask for sample preparation >>(ashing). >> >> Could someone describe this type of flask? What is its purpose? Are >>there any recent articles or references for this flask for further >>reading? > >The Schoeniger flask is named for the developer of the procedure: > Professor Wolfgang Schoeniger, a very competent microanalyst. > >The original was nothing but an Erlenmeyer flask and it was used for >determining elements in organic compounds. Specifically chlorine but >also adapted for other elements. The Quickfit Catalog calls it Schoniger, and references A.M.G.MacDonald in Analyst v.86 p.1018 ( 1961 ) [ Wonderful entertaining, nostalgic commentary deleted ] Yes, and the most common variant in the petroleum industry moved from a 500ml conical flask to a 1 litre flat-bottomed round flask = bigger bangs... I've used the technique for sulfur, chlorine and phosphorus contents of a whole range of petroleum products, and it definitely is one of the more fun analyses - watching the paper burn so brightly. >Sometimes things don't go as planned. So if: >A. Black unburned material is present go back to step one. >B. Flask explodes. C. Paper burns in wrong places and falls into the solution, ( very common in our lab ). D. Stopper leaks ( after a while the ground glass joint tends to distort slightly ) >Now for you young'uns that procedure for analyzing organic compounds >for chloride might not be a big deal but you should keep in mind that >this simple procedure replaced combustion procedure using a Parr Bomb* >containing several grams of sodium peroxide. The method became the standard method for S, Cl, P in mineral oils. It could be quick - about 30 mins for two. I think it is still used - The methods I followed were either ASTM or IP ( Institute of Petroleum = UK ), the IP method numbers were 242, 244, 245 - from memory :-). The technique is often just called flask combustion, rather than oxygen or schoeniger flask combustion. Parr bombs are OK, but bonb calorimeters are also fun - they come with a 10 metre extension lead for the ignition switch ( for the fainthearted/sensible souls who wanted to stand in the next laboratory ). Bruce Hamilton
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