Dear Duco,

As you mentioned, NaOH does not react with 95% or 100% ethyl alcohol since NaOH is not efficient (strong enough) base to abstract a proton from ethanol (this proton is not acidic at all, it is almost neutral). The white precipitate which turned to brown is NaOH that got precipitated during the reaction standing. Generally, you should observe a white precipitate, however, if there is a tiny impurities that are oxidized they can give the brownish color.

Sodium ethoxide can be made by reacting sodium metal or sodium hydride with absolute ethanol.

Hoping this will be helpful,

Rafik

Dear Duco,

As you mentioned, NaOH does not react with 95% or 100% ethyl alcohol since NaOH is not efficient (strong enough) base to abstract a proton from ethanol (this proton is not acidic at all, it is almost neutral). The white precipitate which turned to brown is NaOH that got precipitated during the reaction standing. Generally, you should observe a white precipitate, however, if there is a tiny impurities that are oxidized they can give the brownish color.

Sodium ethoxide can be made by reacting sodium metal or sodium hydride with absolute ethanol.

Hoping this will be helpful,

Rafik

(Apologize for the lengthiness of my comment!)

Dear Rafik, [hello, dear Duco !],

thank you for your statement.

I have to remember my procedures (which I used to generate sodium ethoxide after MAYOR et al. 1961*) / LANE & EUROPA,1965**) in the late 1980ies)..

but it might be / this is  the cause I have found metallic sodium (shielded by anhydrous mineral = paraffin oil) in the chem-board of the EM-Lab I worked until Dec.2015.

*)see: https://www.researchgate.net/publication/9797704_A_simple_method_for_removing_resin_from_epoxy_embedded_tissue_J_Biophys_Biochem_Cytol_9909-910;

**) see: https://www.researchgate.net/publication/19007224_Differential_staining_of_Epon-embedded_tissues_for_light_microscopy or -easier- for the pdf: Journal of Histochemistry & Cytochemistry, @ http://jhc.sagepub.com/content/13/7/579

Cf. also: by HOROBIN RW & PROCTOR J, in Journal of Microscopy, Vol. 126, Pt 2, May 1982, pp. 169-172. see: http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2818.1982.tb00367.x/pdf (only PPV or: http://www.readcube.com/articles/10.1111%2Fj.1365-2818.1982.tb00367.x

or:  by  Jarvis LR, to be found at (unfortunately only PPV):

http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2818.1975.tb04042.x/abstract

The method itself ( also with the use of metallic sodium ) is described also in:  Fluorescence Immunohistochemistry by Confocal Laser-Scanning Microscopy for Studies of Semi-Ultrathin Specimens of Epoxy Resin-Embedded Samples, by Shin-ichi Iwasaki and Hidekazu Aoyagi, cf. http://cdn.intechopen.com/pdfs-wm/15807.pdf : 

Preparation of tissue p.196, and p.197 in (citation):

***) NB: if I remember correctly, it was always 100% "absolute ethanol" which had to be added, not 96 or 95%.

Also in wikipedia  https://en.wikipedia.org/wiki/Sodium_ethoxide  as base  of the reaction with EtOH is mentioned metallic NaOH.  But additionally, another sentence  say: (CIT:)"An alternative, cheaper route involves the reaction of sodium hydroxide with anhydrous ethanol. This reaction suffers from incomplete conversion to the alkoxide, but for less stringent applications, full conversion is unimportant. The salt product may be purified by precipitation in a solution of anhydrous acetone[4]" See also wikipedia/< sodium > for reaction of metallic sodum with ethanol or alcohols in general.

I have noted also a brown solution (guessing it to be a kind of oxidation or impurity reaction) as the end product (after "ripening" of the absolute ethanolic solution  with "oversaturated NaOH". Nevertheless the solution which formed did its job in removing at least part of the epoxy-resin to be able to perform histochemical as well as also IHC-techniques (at least if resin sections were treated and afterwards were "washed" properly .

Best regards, Wolfgang

Article A simple method for removing resin from epoxy embedded tissu...

Article Differential staining of Epon-embedded tissues for light microscopy

Dear RG-helpers. Thanks for all the answers provided. I found out it was cheaper to order the sodium ethoxide directly from a chemical company. This is cheaper and more save then to make it myself. A little lazy, I admid :)

Dear Vladimir: seconding your opinion....(as always:   it becomes humdrum...)

Thanks to Duco....

Best regards,

Wolfgang

Lieber Vladimir / dear Vladimir,

es war mir ein Beduerfnis .../ it was a need for sameness...

Interessant zu lesen dass (kinder) Dermatopathologie zu Deinen Interessen gehoert... schau bitte einmal auf: find: www.scur.org..?  Beste Gruesse und Wuensche, Wolfgang

To all readers in RG:

Not only the downvoting of two specific replies is interesting (also its actual application: 2 times for Rafik KARAMAN, 1 time for W.M.) ...also the

fact that  (9) answers tothe thread are indicated but only 6 answers are shown.

I know that at least two answers from Vladimir Dvoryanchikov  are lacking, a colleague who's profile /personal RG-account seems to be deleted  as a whole:  according to my record keeping: 

Re 04:  2016-05-02 is lacking / is not diplayed:

Notification sent Tuesday/Di 26.01.2016 20:26 by: ResearchGate : New answer by Vladimir Dvoryanchikov added to: 'What happened to the Alkaline ethanol and it turned dark brown?'

Re 06:  2016-05-02 lacking / is not diplayed:

Notification sent Thursday/Do 28.01.2016 20:56 by: ResearchGate : New answer by Vladimir Dvoryanchikov added to: 'What happened to the Alkaline ethanol and it turned dark brown?' 

Re 08:  2016-05-02 lacks / is not diplayed:

Notification sent Friday/Fr 29.01.2016 00:15 by: ResearchGate

New answer by Vladimir Dvoryanchikov added to: 'What happened to the Alkaline ethanol and it turned dark brown?'

As of my (former as well as actual!) understanding (for scientific and or citation reasons) it should be guaranteed that at least TEXT of Reply will be provided / rendered accessible within the thread (usually there was indicated:  "DELETED" and no indication of  a name).  

ResearchGate changing premise???