Reef Chemistry Question of the Day #160 Reading a Floating Glass Hydrometer

[Randy Holmes-Farley]

Reef Chemistry Question of the Day [HASHTAG]#160[/HASHTAG]

The picture below is a picture I took of a floating hydrometer in tank water.

Which value is closest to the correct specific gravity reading of this hydrometer?
A. 1.0255
B. 1.0261
C. 1.0265
D. 1.0271

Good luck!



























.

 

[gfox]

c

 

[JimWelsh]

C. 1.0265

 

[Downbeach]

C

 

[jsker]

B

 

[KingBlingTX]

C

 

[dallasg]

B

 

[soeminpaing]

D

 

[beaslbob]

D

 

[Randy Holmes-Farley]

And the answer is...C. 1.0265

To read the liquid level in this situation, you ignore the meniscus (the water creeping up the hydrometer) and try to visualize straight across the level of the water surface.

When I do that it looks to be around 1.0265. It's hard to judge from this picture alone since you cannot see the 1.027 line, but in reality, it was closer to the 1.0265 than the other answers.

 

[redfishbluefish]

I'm sorry, I've gotten to the party late on this one. I say the answer is C!

Actually what I wanted to mention is the hydrometer I used back in the day had a temperature requirement. There was no mention of the temperature of the sample, and if it was at the specific need of the hydrometer. I can't remember what temp my hydrometer use to be read at, but I know it was in the 60's somewhere, which I always found odd.

 

[beaslbob]

And the answer is...C. 1.0265

To read the liquid level in this situation, you ignore the meniscus (the water creeping up the hydrometer) and try to visualize straight across the level of the water surface.

When I do that it looks to be around 1.0265. It's hard to judge from this picture alone since you cannot see the 1.027 line, but in reality, it was closer to the 1.0265 than the other answers.

I call trick question.

but good question anyway

 

[Perculap]

And the answer is...C. 1.0265

To read the liquid level in this situation, you ignore the meniscus (the water creeping up the hydrometer) and try to visualize straight across the level of the water surface.

When I do that it looks to be around 1.0265. It's hard to judge from this picture alone since you cannot see the 1.027 line, but in reality, it was closer to the 1.0265 than the other answers.

-meniscus

You have inadvertently answered another lingering question of mine, lol. I always wondered about the correct level to use in sample vials. I will now ignore the meniscus!

 

[redfishbluefish]

-meniscus

You have inadvertently answered another lingering question of mine, lol. I always wondered about the correct level to use in sample vials. I will now ignore the meniscus!

NO! When measuring volume, you want to read the bottom of the meniscus.

 

[Randy Holmes-Farley]

NO! When measuring volume, you want to read the bottom of the meniscus.

One could interpret what he said about ignoring it as being the same as reading along the bottom, flat to the water surface.