Unexpected problem with refractometers... lol

[leptang]

Randy, sometimes those precise scientific instruments can be a problem. That's why I take my seven dollar, 15 year old swing arm hydrometer to a coral reef and jump in the water with it. Then I mark a line on it where the thing is floating and use that forever. No testing, no calibration, no nothing but seven bucks and $5,000.00 to get to a coral reef. Simple.

I did the same... But make sure you heat the saltwater to the same temperature as your tank, specific gravity changes in different temperatures.

 

[DLHDesign]

OK I give up. Where do they get that in the ocean?

Seemingly; rain water. From what I've read (in the link provided and elsewhere), they can "siphon off" the top layer of water as it rains - before the water has a chance to mix overly much. With frequent enough rains, this can last them days - or even weeks. They also do swim up into rivers until they reach freshwater to drink when they are near shore.

Interesting creatures, that's for sure. I think that some of the most fascinating creatures are those who live on such "boundary" areas - where they are neither fully of one nor the other. Mammals that swim, Birds that don't fly, etc. It's like we're seeing a snapshot of evolution in motion...

Oh - and very cool that your hydrometer is marked (from what I understand) with the salinity levels of different areas of the ocean! I'm looking forward to my next trip somewhere tropical so that I can take some on-site measurements and, hopefully, even bring some water home for comparison with all the various test kits...

 

[Paul B]

DLHDesign, I never heard that, thanks I will have to look in to it. I know if you put a hose into the water they will drink from it all day but you are not legally allowed to do that. I guess they don't want the germs from their mouth going on to the next manatee. :rolleyes: Now for those whales :eek:

 

[Paul B]

I did the same... But make sure you heat the saltwater to the same temperature as your tank, specific gravity changes in different temperatures.

The tropics are already at the correct temperature so when I jumped into the water I really didn't have to heat it. :D

 

[jason2459]

OK I give up. Where do they get that in the ocean? I have followed them and swam with them for a few days and never saw them coming out of the water for a drink, but I think, at night they crawl over to a swimming pool so they can get a drink of fresh water and maybe take a bath. :D
Or maybe they get it from the same place dolphins,whales and seals get it. Poland Spring. :rolleyes: LOL

At least in the Bay side and near shore ocean side there's run off and the everglades actually push freshwater springs up and then there's people that feed them from the docks with hoses and vegetation which they aren't supposed to do. If they go up further they will hit freshwater. I grew up with them. :) Very cool animals and extremely slow moving. They get chopped up by boats all the time.

Used to be a LOT more freshwater springs before they put the canal system in. "Pirates" and ship goers used to fill up their freshwater reservoirs from them.


Edit: oh and for them besides actually drinking freshwater and other mammals in the sea their main source of water would be from the foods they eat.

Edit edit:
Q. Do manatees drink salt water?
http://www.savethemanatee.org/faq_salt_water.html

 

[leptang]

There is another unexpected problem with refractometers is when you calibrate them under one light and test it under another light source it will be off

 

[Paul B]

Very cool, I didn't know that about manatees. Thanks

 

[GoVols]

Imo worth the 7 bucks

Lol,
I'll sell ya some 1.025 at 7 bucks a "jug"+ shipping & handling :D

 

[Myka]

So, when making a refractometer calibration standard, is it better to spend money on a good quality digital scale or on good quality calibration weights for a cheap scale?

I think what I'm going to do is buy a Red Sea seawater refractometer and then I can calibrate at 0 ppt with distilled water, and also at 35 ppt with Pinpoint seawater solution. This combo should alert me if either the refractometer is not operating correctly or if the 35 ppt solution is off since a true seawater refractometer should be able to be calibrated both ways correctly.

 

[Randy Holmes-Farley]

So, when making a refractometer calibration standard, is it better to spend money on a good quality digital scale or on good quality calibration weights for a cheap scale?

lol I have no idea, but I'd guess the weights.

 

[AllSignsPointToFish]

I bought this digital milligram scale off of Amazon for about $25. It comes with two 10 g weights for calibration. Used it to make 20 mL of refractometer calibration solution, and it worked like a charm. Seemed to me light a good compromise on price point.

https://www.amazon.com/American-Wei...31523&sr=8-3&keywords=digital+milligram+scale

 

[Myka]

I bought this digital milligram scale off of Amazon for about $25. It comes with two 10 g weights for calibration. Used it to make 20 mL of refractometer calibration solution, and it worked like a charm. Seemed to me light a good compromise on price point.

Did you see the link I posted regarding calibration weights? Cheap ones may be off by 20%! Cheap ones are pretty much good for nothing.

I have cheap digital scales - a small one for mg and a kitchen scale.

lol I have no idea, but I'd guess the weights.

That's what I'm think too! The calibration solution is only as good as your measurements! I think I've figured a work around though - I'm going to buy a Red Sea seawater refractometer which can be dual-calibrated at 0 ppt with distilled water and 35 ppt with seawater solution. If the dual-calibration doesn't agree then I know either the solution is off or the refractometer sucks. [emoji38]

 

[AllSignsPointToFish]

Did you see the link I posted regarding calibration weights? Cheap ones may be off by 20%! Cheap ones are pretty much good for nothing.

I have cheap digital scales - a small one for mg and a kitchen scale.

That's what I'm think too! The calibration solution is only as good as your measurements! I think I've figured a work around though - I'm going to buy a Red Sea seawater refractometer which can be dual-calibrated at 0 ppt with distilled water and 35 ppt with seawater solution. If the dual-calibration doesn't agree then I know either the solution is off or the refractometer sucks. [emoji38]

Yes, that is possible, but the calibration solution specific gravity measured exactly as predicted (by Randy) on my refractometer. Either the scale is right or that was an incredible set of coincidences to have the digital balance and refractometer error yield the proper measurement result :)

Also, I have access to high precision digital scales at work that are NIST certified, so I can check my weights anytime if needed.

 

[Myka]

Also, I have access to high precision digital scales at work that are NIST certified, so I can check my weights anytime if needed.

Could you do that please and report back? :D I'm curious just how accurate the cheap weights are. The allowances are HUGE, but are they actually off by much?? Tough to say without checking.

I just checked back on Amazon and the F1 grade set I was looking at has gone up in price from $150 to over $600. dangit. Amazon is weird like that.

 

[AllSignsPointToFish]

Could you do that please and report back? :D I'm curious just how accurate the cheap weights are. The allowances are HUGE, but are they actually off by much?? Tough to say without checking.

I just checked back on Amazon and the F1 grade set I was looking at has gone up in price from $150 to over $600. dang. Amazon is weird like that.

I will definitely try to do that this week. I suspect that the deviation will be small even though the allowable tolerances are large. Shouldn't take more than 10 minutes in the lab :)

 

[AllSignsPointToFish]

FWIW, I places both weights on the balance and it read 19.999g against a nominal value of 20g :)

 

[GoVols]

FWIW, I places both weights on the balance and it read 19.999g against a nominal value of 20g :)

lol,
That's almost... within Brightwell's specs, regarding their neomarine salt mix. :D

AllSignsPointToFish, Please don't hurt me! :eek:

 

[AllSignsPointToFish]

lol,
That's almost... within Brightwell's specs, regarding their neomarine salt mix. :D

AllSignsPointToFish, Please don't hurt me! :eek:

Hahaha! close enough for government work ;)

 

[Myka]

I will definitely try to do that this week. I suspect that the deviation will be small even though the allowable tolerances are large. Shouldn't take more than 10 minutes in the lab :)

Did you get a chance to test the weights at the lab?

 

[805reef]

Can I just go to the beach and get a cup of salt water and use that calibrate my refractometer?