# How do I read my hydrometer?



## Vance G (Jan 6, 2011)

I cannot answer your questions I just want you to be aware that hydrometers for different purposes are scaled differently. I applaud your being careful. Find the MSDS data for your product. It might help.


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## minz (Jan 15, 2011)

I actually picked up a MSDS before the product. I was in semiconductor industry for about 8 years and have more than a healthy respect for the acids. Hand pouring and mixing was simply not done, eventually you will make a mistake so I am checking and double checking every item and every fact. I keep water nearby, check my exit routes, PPE and follow as many safety rules as I can. 
The missing part is the strength of the acid. I would hate to be taking chances and harming my bees simply because I am not correctly interpreting my test results.


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## Ben Brewcat (Oct 27, 2004)

I would read that as 1.160.


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## Deezil (Jul 1, 2013)

In winemaking, the hydrometer is read at the lowest level (meniscus). The surface tension of water will cause the liquid to "stick" to the sides of the hydrometer, throwing your reading off by 0.002 - 0.004. I dont know how much of a big deal it is here, because I really have no clue whats going on (advanced winemaker, spankin' new beekeeper).. Also, you want to read the hydrometer from a level that is flat with the surface of the water, instead of looking down on it here as the perspective can make a difference; just thought I'd throw it out there, as I said, I dunno how important that all is..

With winemaking, the hydrometer is measuring the amount of sugars within the solution. Hydrometers measure the weight of a solution, generally compared to that of water (1.000). The more TDS (total dissolved solids) that the solution contains, the higher the reading. With alcohol weighing less than water, winemakers also see values less than 1.000 (down to 0.990). But we measure acids differently.. 

pH meter would tell you the strength of the acid, while a "titretable acidity kit" would tell you the amount of acids present, expressed generally in g/L.

Wish I had a better understanding of the topic, so I could help out more, but I just thought I'd toss these few facts out for anyone who happens to come across the thread, even if they're not (the facts) of any help to anyone involved in this conversation lol


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## minz (Jan 15, 2011)

Deezil, very helpful. 
Background: I am using Formic acid to treat mites using the mite Fumigation board as per the West Virginia study. The Haz mat fee is more than the acid for most shipments of ‘tech grade’ acid and the lab grade is 10x the price. I got some from a beek that said he treats using formic acid on a plastic tray not a fume board and his study said to mix it to 65%. He sold me a gallon at his cost to try to treat mites with. Too much Formic will drive the bees right out of the hive and they will abscond. Also the follow up studies have found that too high of percentage actually does not work as well. I am attempting to hit the volume of acid as close to the amount as recommended using an unknown. Using a hydrometer (yes one of the pictures in the Alcohol scale) to determine the percentage of acid.
Product Temp in F	C	SG
Formic acid - 10%	68	20	1.025
Formic acid - 50%	68	20	1.121
Formic acid - 80%	68	20	1.186
Formic acid - concentrated	68	20	1.221


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## loggermike (Jul 23, 2000)

Use a battery acid hydrometer.The decimal is omitted when reading it.


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## Deezil (Jul 1, 2013)

So if I'm understanding right, you have 1 gallon of 65% Formic Acid, and you want to dilute it to 50%?

@ 65%, it has an SG of 1.160
@ 50%, it will have an SG of 1.121
..?

If I'm on the right track, you just need to use a Pearson Square to figure out how much water to add to achieve the determined SG
Copy/Paste from personal wine notes/book (not my pic), adapted to the situation here:

Pearson’s Square









A = Water; 1.000 (0 Brix)
B = Formic Acid; 1.160 (36.8 Brix)
C = Target; 1.121 (28.5 Brix)

D = Water in 'parts'
E = Formic Acid in 'parts'

C - A = E
B - C = D

28.5 - 0 = 28.5
36.8 - 28.5 = 8.3

28.5 parts Formic Acid
8.3 parts Water

28.5 + 8.3 = 36.8 total parts
28.5/36.8 = 77.45% Formic Acid
8.3/36.8 = 22.55% Water

So you would need to add a little under a quart of water to the 1 gallon of Formic Acid, to drop it from 65% to 50%
Hope I was on the right track all this time, lol!


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## sjj (Jan 2, 2007)

Ben Brewcat said:


> I would read that as 1.160.


Relative Density of 1.160 means that the concentration of the formic acid solution is 72.5%.


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## johno (Dec 4, 2011)

One of your photo's clearly shows the SG of the liquid at 1.60 if water is added the SG will decrease and the hydrometer float will sink deeper into the liquid so add a half a pint at a time and resample untill the float sinks to about 1.125. theoretically the temperature of the fluid should be around 70 degrees when it is measured but +- 10 degrees should be OK. I buy it by the pint from a company called Duda Diesel at about 95% strength and dilute it to 50% with a wine making hydrometer, I keep the formic acid refrigerated so when it is measured of and mixed with HBH you hardly smell the volatiles. The system works for me
John


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## Deezil (Jul 1, 2013)

John, just a heads up.. With a winemaking hydrometer, that +/- 10 degrees is actually enough to influence the reading (although I dont know how correct we need to be here, its 0.001 - 0.003 difference temp-depending)

Winemaking hydrometers are normally calibrated for 60F (some for 68F) & anything different needs to be adjusted-for.


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## sjj (Jan 2, 2007)

minz said:


> ... I used the hydrometer looking for 1.110 or greater. It appears to be 1.160 but does anybody know how to interpret the concentration of acid and how to read this? ...



http://http://s1141.photobucket.com...eter/DSCF4659_zpsfce2dced.jpg.html?sort=3&o=1


FormicAcidConcentration[%] = (RD - 1)/0.0022 [%] 

at 20°C

RD means Relative Density or Specific Gravity measured with a hydrometer.

Example:
RD = 1.160
RD - 1 = 0.160
0.160/0.0022 = 72.73


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## minz (Jan 15, 2011)

Thanks sjj, that was so simple I want to think it is wrong but it certainly matched the more complex answers. 
Is there a simple way to determine how much water I need to add to take it to the amount that I need? The hydrometer is tall and needs a lot of room to float. If I could get by without having to mix up a gallon of acid when I only have to do 3 more hives it would help me to not mess with the acid more, and to store less volume of chemicals.
I was thinking of a % like add 25% water, that way I could add the water, HBH, and then the acid to make the correct amount.


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## sjj (Jan 2, 2007)

minz said:


> ... Is there a simple way to determine how much water I need to add ...
> I was thinking of a % like ...



Delta_Water / V1 = C1 x [(C1 - C2) / (C1 x C2)] 

Delta_Water = V1 x [(C1 / C2) - 1]


V1, C1 on the input site are volume and concetration of FA. They are known. 
V2, C2 on the output site. C2 is known.

V2 = V1 + Delta_Water 

(destilled water)


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## minz (Jan 15, 2011)

Thanks everybody. I ran the equations above and I got it to work out with the hydrometer. Sorry to be so anal but the thing was that the container that I was using would only hold just over 6 cups. Too little and I could not read the scale through the side, too much and it risked being difficult to pour or spill. Also like to always add acid to water rather than the other way around.
I took 8 pictures of my final mix and not a single one of them turned out. It was just above the 2 and my mix was 1.5 cups of water to 4 cups acid. I put a cup of water in then trimmed it with the last cup like deezil suggested.


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