Help - Calibration Request

[brians_224]

Thanks for your time.

I'm trying to calibrate my new refractometer. distilled water won't work on this one.

Could some one please measure the Specific Gravity of Heinz distilled white vinegar? I've made two salt water solutions as per randy's recipe - but the inadequacies of my measuring devices leads to two different readings. I found a value in their msds, I'd like to confirm it.

Thanks!

 

[AllenFord_SC]

Do you have a LFS nearby? They should best willing to test it for you.

 

[bertoni]

Hmm, why doesn't distilled water work? Does it not read to 0 ppt salinity? Sigh!

I'd be afraid to use vinegar as a calibration solution, and unfortunately, I don't have any of that brand. I could measure some Safeway brand, if you think that'd help.

 

[brians_224]

Thanks for your posts.

Its one of the Marine Depot refractometers - its supposed to but doesn't calibrate with distilled water. I worked with randy and a few other RC members who had similar problems with the device. If you calibrate to 0 with distilled water, and test my tank water it reads ~1.03 - if I measure using randy's mixture it reads ~1.03 - should read 1.026.

Just trying to find a source of truth.

 

[WaterKeeper]

Calibration of a refractometer, no mater whose, requires that you find a zero point for light refraction. Even if you use tap water you can zero it as the refractive index of seawater is so much higher. I would start believing that your tank S.G. is indeed over 1.030.

 

[brians_224]

Thanks -

Look at this...

 

[bertoni]

Sigh. Well, I'm glad I'm skeptical about aquarium equipment.

 

[dots]

Im curious, whats going on with it? I have one also and seems to be straight foward? Are you calibrating it with the water you are mixing? Is it the same water as you buddies? That is why I like instruments like that, they can be tuned. Why are you using the vinegar instead of the pure water? Are you adding the same amount of salt to exactly the same amount of water for your two samples. The only reason I ask is that it is strait foward physics, ie no moving parts, just a coated prism. If you are sure that you calibrated it correctly, it may be defective. Interesting

 

[brians_224]

I agree the device seems very straight forward. Theres a problem with the 0 point.

When I made my solutions I tried a 2 liter version, and a 1 liter version. I use a kitchen scale for weighing the salt. I think its fine for flour - but not accurate enough for this application. The two solutions are close - but I'd like to find a source of truth.

I chose the vinegar b/c it would be available nationwide, and I found a value in their msds.