tag:blogger.com,1999:blog-4387100009341358284.post1794319128347085606..comments2024-03-12T09:55:15.923+01:00Comments on Curly Arrow: GreaseDaniel Sejerhttp://www.blogger.com/profile/12498255536497699232noreply@blogger.comBlogger11125tag:blogger.com,1999:blog-4387100009341358284.post-25215867083801172612014-02-18T18:10:30.811+01:002014-02-18T18:10:30.811+01:00What is tygon? It's unfilled PVC plasticised b...What is tygon? It's unfilled PVC plasticised by dibutyl pthalate, and is oxygen and water have much higher permeation coefficients than black filled PVC. Tygon is very good at stopping oxygen permeation (but not as good as black PVC), but has very high permeation of water, but still lower than poly(isoprene).<br /><br />The shame is you can't but PVDC (saran) tubing anymore. It has low Bryn Monneryhttp://monodisperse.wordpress.com/noreply@blogger.comtag:blogger.com,1999:blog-4387100009341358284.post-31222221893561602102007-11-19T21:58:00.000+01:002007-11-19T21:58:00.000+01:00As usual, Milkshake is right on. My question wasn...As usual, Milkshake is right on. My question wasn't about the ultimate vacuum of a pump, but the vacuum that is attainable under high vac distillation. I generally use Chemglass (or Ace) stuff as well...and ive been happy with it. Also i was using a small vacuum jacketed vigreux last time when the vacuum was all over the place. but then ive done it the same way (same glassware) before with noAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-4387100009341358284.post-53708747384015447552007-11-19T20:09:00.000+01:002007-11-19T20:09:00.000+01:00The question was about vacuum distillation, not ab...The question was about vacuum distillation, not about max performance of a closed manifold. Normal 2-stage oil pumpms have a nominal vacuum about 0.3 mTorr so I bet you can go lower than 4 mTorr - if you close everything.<BR/> <BR/>In my experience a fractional distillation on higvac (while keeping the vacuum below 100mTorr) can be tricky, even with just a short Vigreaux. Every tiny leak shows. Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-4387100009341358284.post-24939567852282768402007-11-19T02:55:00.000+01:002007-11-19T02:55:00.000+01:00"When one needs to go to such high vacuums (below ..."When one needs to go to such high vacuums (below 0.1 Torr)"<BR/><BR/>0.1 Torr??? I get upset when I can't get my vac. line below 10 mTorr...and in most cases am unable to fully dry my reagents. The most common sources of error for me tend to be moisture in the hoses (heat for several minutes with a heat gun while pumping to remove), poorly greased joints, not having enough liq. N2 in the trapsAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-4387100009341358284.post-55992075117948980632007-11-16T07:28:00.000+01:002007-11-16T07:28:00.000+01:00I don't know what Tygon is made of and it seems pr...I don't know what Tygon is made of and it seems pretty solvent resistant - but the cheap kinds of vinyl tubing contains something like 60% of phtalate by weight and it does dissolve easily. Many companies sell vinyl vacuum tubing and I have seen thick "tears" of dissolved plastic oozing down inside the tubing, brought about by repeated exposure to solvent vapors.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-4387100009341358284.post-75652484515447901842007-11-15T22:23:00.000+01:002007-11-15T22:23:00.000+01:00excellent. i knew between derek (pipeline), danie...excellent. i knew between derek (pipeline), daniel (curly arrow), and milkshake (org prep) my question would be answered in a most satisfactory manner. apiezon H (and L) and Tygon tubing just arrived. Thanks all!!Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-4387100009341358284.post-37374502571639800542007-11-14T12:47:00.000+01:002007-11-14T12:47:00.000+01:00Milkshake is making some very good points. Keep co...Milkshake is making some very good points. Keep connection points to an absolute minimum. Have as few joints as possible and make sure that you get the perfect fit and use the correct Apiezon grease. If you suspect your system is leaking pull it apart and attach the vacuum gauge to the pump. Check the final vacuum. Connect the next bit and check the vacuum again. Keep doing this until you find Daniel Sejerhttps://www.blogger.com/profile/12498255536497699232noreply@blogger.comtag:blogger.com,1999:blog-4387100009341358284.post-14943612264072291352007-11-14T12:43:00.000+01:002007-11-14T12:43:00.000+01:00I don't think the plastisiser came form the Tygon ...I don't think the plastisiser came form the Tygon tubing. To get significant amounts of plastisiser in your sample you need to get the tubing in direct contact with an organic solvent for some time. I have experienced some pretty annoying plastisiser contaminaions over the years. Once some clever individual decided to use rubber tubing when filling the hexane bottles up from the tank. Recently, Daniel Sejerhttps://www.blogger.com/profile/12498255536497699232noreply@blogger.comtag:blogger.com,1999:blog-4387100009341358284.post-69019350250036464722007-11-13T01:23:00.000+01:002007-11-13T01:23:00.000+01:00Curlyarrow: Thank you for the plug. (Also, if the ...Curlyarrow: Thank you for the plug. (Also, if the spam posts are bothering you here, Wordpress has a quite easy-to use and efficient filtering system, and its free).<BR/><BR/>Sometimes the leak in the system is from poorly matching joints. When one needs to go to such high vacuums (below 0.1 Torr) there should be as few connections as possible and as strong pump (=with high pumping speed) as Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-4387100009341358284.post-71276572720545703202007-11-12T22:03:00.000+01:002007-11-12T22:03:00.000+01:00I have in the past used the grease in the syringe ...I have in the past used the grease in the syringe trick, but I am still looking for a way to get the grease in the thing without a high proportion of it ending up on me.<BR/><BR/>(re Tygon: The regional MS facility hereabouts got real tired of analyzing dibutylphthalate for graduate students who were convinced they had discovered some new reaction after finding this unknown in small amounts in Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-4387100009341358284.post-30060157245620135182007-11-12T14:55:00.000+01:002007-11-12T14:55:00.000+01:00We had an issue a while back in one of those under...We had an issue a while back in one of those undergrad lab classes where you have to characterize & identify unknowns. A lot of students ended up with plasticizers, which shouldn't have been their products by any stretch. We think they leached out of the Tygon, but it's also possible that there was some crud at the bottom of the DCM tank in the stockroom--someone from Pharmacy mentioned having Ψ*Ψhttps://www.blogger.com/profile/15089754859676425655noreply@blogger.com