5 replies to this topic

[Hidden Valley Wine]

I need a little help in making sure I have the right mixtures. SO here is what I did. First of all I made a mistake when I started and had to adjust afterwards. Hope I dont confuse you here. I took 5 grams of tartaric to 500ml of distilled water(wasnt thinking) and I also took 8 grams of sodium hydroxide to 500ml of distilled water(still wasnt thinking) for a .2N. I ran a test and it came out at 5cc to (15ml sample) of what I thought was .2N Didnt think to much about it until I ran a test on some wine and needless to say I was way off and new something was wrong. It finally came around to what I had did so I adjusted my mixtures as follows 100ml of distilled water to 100ml of the tartaric solution that I had and did the same to the NaOH and redid the test and came out the same(5cc to the 15ml sample). I then went a step further. I wanted to make a .1N so I took 100ml of the .2N and added 100ml of distilled water. I did the test again, 15ml sample of the 5g/l tartaric solution and it took 10cc of .1N solution to reach my end point. According to my calculation of 75*N*ml of N / ml of sample = 5

So what do you think?? GIVE UP THE CHEMISTRY AND LEAVE IT TO SOMEONE THAT KNOWS WHAT THEY ARE DOING. or did I get lucky in making this stuff. All help will be greatly appreciated.

[sbl]

I need a little help in making sure I have the right mixtures. SO here is what I did. First of all I made a mistake when I started and had to adjust afterwards. Hope I dont confuse you here. I took 5 grams of tartaric to 500ml of distilled water(wasnt thinking) and I also took 8 grams of sodium hydroxide to 500ml of distilled water(still wasnt thinking) for a .2N. I ran a test and it came out at 5cc to (15ml sample) of what I thought was .2N Didnt think to much about it until I ran a test on some wine and needless to say I was way off and new something was wrong. It finally came around to what I had did so I adjusted my mixtures as follows 100ml of distilled water to 100ml of the tartaric solution that I had and did the same to the NaOH and redid the test and came out the same(5cc to the 15ml sample). I then went a step further. I wanted to make a .1N so I took 100ml of the .2N and added 100ml of distilled water. I did the test again, 15ml sample of the 5g/l tartaric solution and it took 10cc of .1N solution to reach my end point. According to my calculation of 75*N*ml of N / ml of sample = 5

So what do you think?? GIVE UP THE CHEMISTRY AND LEAVE IT TO SOMEONE THAT KNOWS WHAT THEY ARE DOING. or did I get lucky in making this stuff. All help will be greatly appreciated.

The first solution you made was not 0.2N--it was 0.4N NaOH -- 1N is 40g/L so 8g in 500 ml is the same as 16g in 1L which is 16/40N or 0.4N.

When you diluted both the tartaric acid and the NaOH by half, the ratio stayed the same--the only difference was you were now dealing with 0.2N NaOH.

The next dilution should have made 0.1N NaOH. Depending on how accurately you weighed the tartaric acid and the volume, you may have a few more significant figures. See chemistry is not that hard!

[Hidden Valley Wine]

Chemistry is not easy, it is made easy by you guys on this forum. Actually this was my second attempt at making NaOH. My first attempt went bad because I had some beakers that I bought from piwine and after I got them they said they were APPROX. on the side so they were not accurate enough to use. I finally broke down and bought some volumetric flask. With the accuracy of them and the help from this forum I think I have enough tartaric solution and NaOH to last a long long long time. My many thanks to all you guys that help out on here. You guys are great. Cheers too all.....

[A_perfect_ashler]

I finally broke down and bought some volumetric flask. With the accuracy of them and the help from this forum I think I have enough tartaric solution and NaOH to last a long long long time.

It wouldn't hurt to test it against some purchased solution. And also do not store it in glass. NaOH reacts with glass changing the normality. If you can find some saran coated plastic bottles use them for storage. Keep them tightly sealed as NaOH also reacts with Carbon dioxide in the air. If there is any precipate in your stored solution after some time it has reacted with either glass or CO2.

Dave Warner

[Hidden Valley Wine]

It wouldn't hurt to test it against some purchased solution. And also do not store it in glass. NaOH reacts with glass changing the normality. If you can find some saran coated plastic bottles use them for storage. Keep them tightly sealed as NaOH also reacts with Carbon dioxide in the air. If there is any precipate in your stored solution after some time it has reacted with either glass or CO2.

Dave Warner

Thanks Dave, Ill keep that in mind. I also like your little story about the honeymoon.

[A_perfect_ashler]

I need a little help in making sure I have the right mixtures. So what do you think?? GIVE UP THE CHEMISTRY AND LEAVE IT TO SOMEONE THAT KNOWS WHAT THEY ARE DOING. or did I get lucky in making this stuff. All help will be greatly appreciated.

Here is some
The usual procedure is to standardize against a primary standard which is made from a chemical called KHP which is a chemical which is stable in air and does not gain weight too fast by adsorbing moisture or water from the air. Sodium and potassium hydroxide are hygroscopic and will adsorb water from the air, so much so that they will eventually dissolve in the water they adsorb. So you cannot get a very accurate solution by weighing it. It needs to be dried before weighing then allowed to cool in a sealed container called a dessicator which contains a water vapor adsorbent such as silica jell. See the lab procedures in the fillowing links. It should be weighed with a scale accurate to four decimals if a gram.

More about KHP:
http://en.wikipedia....rogen_phthalate

Here is a good link to a lab procedure on how to make a standard acid/base solution.
http://icn2.umeche.m.../titration.html
Another
http://www.sci.sdsu....s/2006_Exp2.pdf

Here is a more detailed lesson from Argonne National Laboratory.
http://www.newton.de...3/chem03525.htm
And more:
http://www2.truman.e...ual/pdf/khp.pdf

Check also this thread.
http://www.winepress...showtopic=31111
And this one:
http://www.winepress...showtopic=31608

Fisher scientific has the primary standard KHP for $115.68 for a 100 gram amber bottle here.
https://www1.fishers...amp;fromSearch=
http://www.sciencela.../S/PVAR/SLP2020 has it for $151.24 for 500 grams.
http://www.sciencest...em-Rgnts/C2328# has it for $75.74 for 500 grams.

Dave Warner
PS if you liked my honeymoon story you might like my 'Three drowned mice' story in a past thread, try searching for it or send me a line.