From: Richard Guy Newsgroups: alt.humor.best-of-usenet Subject: [sci.chem] Lab Accidents....... Date: 11 Nov 1996 10:39:05 -0700 Subject: Lab Accidents....... From: rwpick01@ldd.net (Randal W. Pick) Newsgroups: sci.chem All *true* chemists must have had at least one or two spectacular accidents while they were in school learning the science and craft. Here's one of mine (let's hear yours): ACCIDENT #1 COURSE: Quantitative Analysis (sophomore level flunk out course - one rigorous MF! Reduced the number of prospective BS Chem majors from around 150 to around 20). CONDITION: Attending 7:00 am Saturday morning make-up experiment with severe hangover and no sleep. OBJECTIVE: Determine amount of Nitrogen in cow's blood. METHOD: Kjeldahl Determination DESIRED RESULTS: a) Quantitatively transfer accurately weighed dried blood to Kjeldahl flask containing 500 ml of concentrated sulfuric acid. Boil at dull red heat (~600 F) for 1 hour. (I am not kidding) b) Meanwhile assemble rest of apparatus: ~500 ml concentrated NaOH in flask at top of apparatus ready to be dripped into 500 ml conc. sulfuruc acid. (!!!!!!) c) Sidearm from vertical tube is intended to convey ammonia gas into a separate flask of standardized acid after sulfuric acid is neutralized and resulting sodum sulfate/water solution turns strongly basic driving NH3 gas off (from N in blood). d) Backtitration allows calculation of nitrogen (hence protein) content of dead cow's blood. f) Instructor (Dr. Caskey) examines painstakingly ink-written notes, gives student D-. Student is grateful. ACTUAL RESULTS: a) First few drops of NaOH into acid produce really neat fizzing and popping. b) Subsequent drops do nothing. c) Poor hungover student ponders the thermodynamics of concentrated NaOH *refusing* to react with concentrated sulfuric acid. Must be having bad dream. What is entropy? d) After having dripped entire 500 ml of sulfuric acid into 500 ml of conc NaOH nothing has occurred. (Student scratches head, wishes he was synthesizing acetylsalicylic acid instead). e) Student realizes he has mis-aligned vertical tube, allowing conc. NaOH to flow gently down side of vertical tube into conc. sulfuric acid. Result is 500 ml of sulfuric acid has formed layer beneath 500 ml conc NaOH separated by thin film of water/NaSO4. f) Student resists urge to panic and run, leaving this impossible mess to the TA. g) Student tries to salvage experiment by *gently* agitating flask to mix conc. sulfuric acid and concentrated caustic. h) Mixing starts out OK until heat of reaction causes water to boil, rapidly mixing conc. sulfuric acid and conc. NaOH. i) Resulting steam explosion blows dropping funnel off top of apparatus and blows contents of apparatus all over ceiling tiles in a fraction of second. My reflexes are quick enough to note that reaction accelerates exponentially, just like out-of-control reactions are supposed to. Mess is dripping off ceiling tiles all over surrounding (and very busy) laboratory. j) Student calmly and purposefully leaves laboratory for dormitory and crashes for 12 straight hours. k) Student makes F on experiment. EPILOGUE: After graduation (one of eight BS Chems out of graduating class of 5000), ex-student returns to Chem/Biochem department for some paperwork. Secretary remarks "Ooooh! You made a C- in quant! That's good!". Ex-student's mouth drops open, decides on analytical chemistry as profession.