OK, I'll try to make it short
:
-It begins with this post:
Post 503558
(zero_nrg: "Louis Pasteur used a micrscope and tweezers to", Stimulants)and a followup article posted by Rhodium...
-Methyl_Ethyl a few posts later mentions the use of 2 crossed polarized light sources to distinguish between l- and r-isomeric salts as being superior to the mechanic separation by hand.
-Then you question the use of crossed polarized light with the following words:
"why? it should be very easy to separate crystalls in right and left handed ones. (just like you would be able to separate gloves for the right and for the left hand)"-Then Methyl_Ethyl explains to you that it just is the superior method.
-You answer with (drumroll)
"i wasn't suggesting that it's easier to go by geometric criteria" (tadaa - sounded like you at least suggested it "should be very easy", though...), and clarify about having meant that mechanical "per view" separation is possible with some salts, and that Pasteur used this technique. As "proof" you give the bad quality of his microscope..
(there's no logic behind that - it is in fact a proof
for crossed polarized light isomer identification and
against mechanical sorting at that time, if you think about it...)
Nothing new so far...
-Now I tried to explain that polarized lighting has the advantage of being applicable to all optically active salts (not only tartaric, but also visually not distinguishable hydrochlorides of optically pure d/l-isomers for example). To do so, I explained how polarimetric identification with 2 crossed light sources works.
-You claim that I said something wrong and present hexagonal crystals standing on their small side as an argument. You say that with big crystals, mechanical separation is easy and that tartric acid gives distinguishable crystal modifications (D'oh!)..
OK let me reiterate what I said before in four short sentences:
-crossed polarized light identification is more generally applicable and therefore advantageous compared to visual/manual separation with microscope/tweezers.
-Although seeming not in agreement with what I said, you still have given no reasonable exp. about which novel information you originally wanted to add to this thread?!
-It was already said that tartaric gives crystals with differing physical properties,
-and it was already mentioned that Louis Pasteur used the tedious "by hand" method on tartaric.
So far the important facts I re-checked....
"thanks for trying anyway..."Well, you're welcome - even more if you try to understand what others write next time,
before criticizing them...
(dividing a bunch of salt into optically pure isomeric salt modifications by hand can be a good occupation for the long winter months - hypo sittin there with his giant magnifying glass and a needle, while others just illuminate the scene correctly, take what they want and leave back the remainder - but hey! it's your time...)
indole_amine