hydrometer versus weighing liquid

[bobtheUKbrewer2]

I have some extremely accurate balance scales. Would it be feasible to pipette say 100 ml of fermented wort into the scale pan and note the weight to exactly balance it. Assuming wort is 1.010, 100 ml would weigh 101gm. Scales are definitely good to weigh half a gram.

I have been looking in the UK for a short range hydrometer, but cannot find one.

 

[danb35]

Certainly possible, if you trust your volume measurements to be accurate to +/- 0.1%. Hydrometers typically read to three decimal places, so you'd losing a fair bit of precision with this technique.

 

[bobtheUKbrewer2]

But hydrometers that measure 0.980 to 1.180 on 5 inches of scale cannot be that precise. Also air bubbles clinging to hydrometer can introduce inaccuracy. I will increase the volume of wort to 500 ml to increase accuracy as .1% of 100 ml is 0.1 ml. I will use a burette probably if I go to 500 ml. Thanks.

 

[danb35]

...and actually, I misspoke--the hydrometer I use does measure to three decimal places, but in increments of .002. Taking your numbers, that's 0.050", or about 1.25 mm, per increment, which seems easily achievable.

What you're suggesting is fundamentally sound--if you have an accurate weight, and an accurate volume, computing the density is child's play. And if you have the lab glassware to use, you probably know better than I how to determine the degree of uncertainty in your computed values.

As another option, you could always use a refractometer...

 

[broadbill]

Is this level of precision necessary? I've considered my hydrometer to be at best only a ballpark for multiple reasons (temp correction, bubbles, being able to see the meniscus, etc. etc.). If I'm good to the nearest 0.005, that is good enough for me....

 

[BackAlley]

I've often wondered if you could track the fermentation by weight of the fermenter instead of having to grab samples risking contamination.

 

[ajf]

I have some extremely accurate balance scales. Would it be feasible to pipette say 100 ml of fermented wort into the scale pan and note the weight to exactly balance it. Assuming wort is 1.010, 100 ml would weigh 101gm. Scales are definitely good to weigh half a gram.

I have been looking in the UK for a short range hydrometer, but cannot find one.

Try www.hopangrape.co.uk or
www.camlab.co.uk

-a.

 

[bobtheUKbrewer2]

As another option, you could always use a refractometer... danb35

See my recent thread about how to calculate ABV with a refractometer. I was very firmly told that a refractometer is useless once alcohol is in the fermenting wort.....

 

[SpeedYellow]

IMHO a better idea is to use your equipment to create a couple sugar solutions to calibrate the hydrometer.

 

[smyrnaquince]

I've often wondered if you could track the fermentation by weight of the fermenter instead of having to grab samples risking contamination.

I think you'd have to also track the volume in the fermenter. I haven't looked at the chemical equations, but I doubt you'd lose that much mass from the CO2 gas-off and that the larger effect would be the change in volume due to more-dense sugary word being replaced by less-dense alcohol.