Sciencemadness Discussion Board

Instrument patents

If_6_was_9 - 4-4-2004 at 11:50

You can usually find old/antique lab equipment on Ebay or other places, for example, polarimeters, refractometers and scales or balances. I looked up some old patents relating to these instruments:


Polarimeters found in class 356 subclass 367:

US844012
US1072166
US1525145
US2310623

Polarimeter patents which show analyzer/detector arrangements:

US2412074
US2583186
US2923198


Refractometers found in class 356 subclass 137:

US2080841 BAUSCH & LOMB
US2574734 BAUSCH & LOMB Abbe type
US2633052
US2729137
US2740320 BAUSCH & LOMB
US6172746
US6480347 prism positioning


Analytical balances:

US1203686 detailed
US1551726
US336546
US1332783
US1387998
US5927989 4 pan algebra balance
US1258009 chain detail

Beam with hanging pan:

US3082833 Ohaus knock-down
US837374
US4453610
US4836315
US533166

miscellaneous:

US1015739 spoon balance
US2228872 balance with crucible and burner
US4139068 short, beam in front

http://gb.espacenet.com/

or

http://www.geocities.com/dritte123/PSPF.html

[Edited on 4-4-2004 by If_6_was_9]

If_6_was_9 - 4-4-2004 at 13:00

US2047561 reminds me of a home made refractometer I saw in an article before. I think it was in Journal of Chemical Education.

If_6_was_9 - 8-4-2004 at 16:20

US2310623 dislcoses a polarimeter which includes the use of a polarizing strip 23 and a sheet 21 set at a 20 degree angle to strip 23. Sheet 27 is the analyzer. Note on page 2 column 2 lines 65+ where it says:
Quote:

The smaller the acute angle between the axes of elements 21 and 23, the greater the accuracy of the measurement but the less light will be transmitted. It has been found that by making the angle 20 degrees the best compromise between light transmission and accuracy of measurement will be obtained.




In Figure 1 of US2923198 you can see side by side Polaroid sheets 16 and 17 are polarized at a 45 degree angle to each other.

[Edited on 9-4-2004 by If_6_was_9]

If_6_was_9 - 24-4-2004 at 15:47

There's a lot of old instruments here:


http://www.humboldt.edu/~scimus/index.shtml

polarimeter

Magpie - 15-2-2005 at 10:37

I just purchased a vintage polarimeter off ebay for <$200. The light is brought into the instrument through an adjustable mirror. It doesn't have a light source so I'm looking for a cheap one from local sources. I have identified a Phillips Ceramalux clear 35w high pressure sodium bulb for $17. Would this do the job? Do I need a filter to get the 589 nm wavelength (sodium "D" line) isolated? Any help would be very much appreciated. - Magpie

Note: Upon further investigation I am happy to find that my polarimeter has an internal filter to isolate the sodium "D" line. I should have realized this when I looked through it and saw an orange light when using a regular incandescant lamp. But I still need to buy a sodium bulb for rotation angles > 12 deg.

[Edited on 15-2-2005 by Magpie]

Magpie - 20-2-2005 at 20:55

For my polarimeter I ended up buying a 35w high pressure sodium lamp complete with ballast and igniter (a bargain at $39). I replaced the heavy outdoor housing with a homemade one to reduce weight and size. I mounted the light on the side in a horizontal position as this keeps the liquid sodium from pooling in the bottom when the lamp is turned off. The lamp puts out a source of orange light which I believe is nearly monochromatic at 589 nm wavelength.

If a person could collect the old lamps when a city is relamping he would potentially have a source of sodium - but it's probably a very small amount/lamp.

I tested the polarimeter with a 0.3g/mL and 0.1 g/mL sucrose solution. I read 66.3 deg and my reference says 66.7 deg for the specific rotation so I am very pleased. I found that when I tried the incandescent lamp on the strong solution I could get within +- 2 deg, however.

My goal is to have a few relatively cheap instruments and wet chemistry methods to verify purity and/or measure concentration of chemicals I synthesize. I already have melting point glassware. Now I am looking for a cheap Abbe' refractometer (<$200). This may take some patience.