Refractometer Calibration Solution - anyone?

EvilMel

is a serious goby fanatic
Hey guys, Dave Sease asked me to make a calibration solution for his refractometer (he asked a few weeks ago and I finally actually got down to doing it).

I have made the solution as follows:
35 g NaCl into water with a total volume of 1 liter.

I believe that gives 35 parts per thousand, which corresponds to 1.025 on your refractometers, right?

Does anyone else want some of this solution?

I made 500 ml and I have dispensed it into 10 ml aliquots.

I am working down at the Coral Reef on the weekends now and I will bring it with me on Saturday/Sunday. I'll be there all day both days so if anyone wants a 10 ml tube of it, just come down and I'll give you one. I made these to the best of my ability and am hoping my calculations are accurate but I can't absolutely guarantee that they're perfect.

I'm not charging for them or anything. I just figured you guys might be interested to know how accurate your refractometers are!
 

cee

New member
I'd like an aliquot or I can just bring my refractometer and a few drops should suffice. 35 ppt is 1.026 I believe. Can you weight the salt to +/-0.01 grams accurarcy? Thanks.

Dave
 

fishdoc11

catch and release
Team RC
Oh Oh Me Me!

Can I have one please? I'll trade you some mysis shrimp for it:)

Will you be at the meeting Mel?
 

EvilMel

is a serious goby fanatic
Yeah Dave. It was something like 17.5125 g then I filled the graduated cylinder up to 1 L.

The thing I read said that 1.025 equalled 35 parts per thousand but I am not 100% certain what I read was accurate since I didn't actually make the calculation myself.

Chris, I work there on the weekends now so yeah, I'll be at the meeting. No need for trades but I would love to have my mysis shrimp!

Jeff just come by the store this weekend, no problem!
 

EvilMel

is a serious goby fanatic
Nice!

So yeah...I didn't write down the exact number but it was something similar to what I said.
 

macclellan

New member
Thanks for the offer, Mel. I'll stop by today to pick up some fancy water. I've been wondering how well calibrated mine is.

cheers,
joel
 

EvilMel

is a serious goby fanatic
Turns out that my refractometer was way off...1.022!!

But the one at the Coral Reef was 1.025, so that's pretty accurate.
 

cee

New member
Mel:
I got my solution today, thanks. My refractometer was off even though it was recently calibrated. Just out of curiosity, did you use a 3.65 weight percent sodium chloride solution, made by dissolving 3.65 grams of sodium chloride in 96.35 grams (mL) of purified freshwater? Just wanted to be sure before recalibrating mine. Thanks again!

Dave
 

EvilMel

is a serious goby fanatic
I said earlier that I weighed something like 17.5 g of NaCl then filled the graduated cylinder up to 500 ml (so it wouldn't be a full 500 ml, just enough to make 500 ml total).

I can remake it and tell you the exact weight out to four decimals if you want or you can make it yourself and not use the free stuff I'm trying to give out.
 

cee

New member
Ah, that explains it then. That's about a 3.5% by weight ratio which, according to Randy, is 33 PSU (effectively ppt) or, as you stated earlier, 1.025 specific gravity. Thanks for the clarification; I should have read above before questioning.

Dave
 

Runner

New member
If you still have a tube left, I'd like one. Or just a few drops at the meeting next week. Thanks, Mel.
 

ct_vol

Reefing On My Mind
Team RC
It was down at the CR last I was out there Scott... :)


My refractometer was about spot on... Of course I've only checked using specific gravity... Not sure if thats a good or bad thing... :rolleyes: Everything is alive though... :D
 

EvilMel

is a serious goby fanatic
Scott, yes...go ahead down there and grab one. I left them with Dave and Russell. They are behind the counter on the left, on top of that shelf on the left.
 
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