Immersion öl

[Rene]

Hallo,

Our oil (Cargille) turned cloudy in the suspension bottles. Type A (thin) more so than Type B (thick). It could be either the bottle material (PE) or the exposure to (sun) light that is causing cloudiness (bottles generally last years on the bench). Is there someone with the same experience? What bottle (material) should I be using?

From the MSDS: Ingredients are HYDROGENATED TERPHENYL , TERPHENYL, NATURAL HYDROCARBONS, POLYBUTENES. That should be pretty inert, or not?

Thanks,

René

Apologies for my use of english, replies in Deutsch appreciated.

[jochen53]

Hello,
in order to achieve the high refractive index of about 1.518 aromatic compounds or higly chlorinated substances are required. In former times polychlorinated biphenyls (PCB) were used mainly mixed with di-n-butylphthalate later different grades of chlorinated paraffins were in use also mixed with phthalates, but nowadays these compounds are considered as reproductive-toxic. The terphenyl and hydrogenated terphenyl give a high refractive index, these fluids are mainly used in the chemical industry as heat transfer fluids for very high temperatures. The polybutene is used to give a higher viscosity. The whole combination is optimised to adjust the refractive index and the Abbé number of the oil. The solubilty of polybutenes is sometimes dependent on the molecular weight or even the molecular weight distribution, there are many grades of polybutenes with different molecular weights on the market. Polybutenes are unsaturated compounds that contain some double bonds and can be susceptible to oxidation by air and UV-light which gives a little yellowish colour. Normally PE (HDPE or LDPE) does not contain plasticisers or other additives that can be extracted by oils. Another source for a cloudy oil could be a small content of humidity. If you warm up the oil (best would be in vacuum) the turbidity should disappear.

[Rene]

Thanks Jochen!

Cargille replied to me, their stuff is indeed light sensitive. However, they sell their stuff also in small (10ml) transparant squeeze bottles; the larger quantities (25ml and more) come in brown bottles.
I'll get small opaque LD-PE bottles for the lab and a new batch of oil.

With 200ml oil leftover, it won't hurt to try your other suggestion and leave it at 120oC for a night and see what happens.

Best wishes, René

[Rene]

Humidity was indeed a good suggestion Jochen. I've left it during the afternoon at 150oC, and the cloudiness partly disappeared! The colour is much more yellow than the leftover in the original (brown) bottle.
Besides of the humidity, something else is happening as well: some of the oldest bottles (5 yr on the bench, but never in full sun) developed gummi deposits on the bottom of the bottles.  Hmmm.

The stuff is cheap, so I´ll throw it out anyway.

Thanks for your insights,

René