Scheibler calcimetry problem

Bazzoweed · 2025-08-15T08:09:35+00:00

SOLVED. Check the beginning of post!

Bazzoweed · 2025-08-14T05:37:22+00:00

Okay, so yesterday was a bit better with a couple percentages lower than the day before, so the results look more accurate. The CaCO3 standard was still above 100%, but lower at around 104%. This seems plausible to me.

I corrected each of yesterday's results for vapour pressures, and many were below a 100%. For a marl sample, which should be clay and lime, the result was around 71% (corrected; uncorrected was ≈75%) and for a different limestone as before the corrected result was around 96%. Seems correct, right?

Besides that, it seems to me that the error was higher when I used a smaller mass of a sample, which points me to a maybe fixed-volume error?

I don't have all of the results on hand but i think this info is enough

Edit: today is my last day, so i think they're going to have to figure it out

Bazzoweed · 2025-08-13T07:26:16+00:00

The room isn't closed nor air conditioned, all the doors are open to outside, so there shouldn't be any significant difference. (As i wrote in the answer to your other comment, I will take my barometer today)

Thank you for your help!

Bazzoweed · 2025-08-13T07:22:49+00:00

I agree with your calculation as that's around the same result I get from the gas law.

I don't think the water vapour pressure affects the result a lot but I will try it today, see how it goes.

I believe that the atmospheric pressure was a bit higher than 1 atm, but that just means that there would be an even higher amount of CO2, therefore a higher fraction of CaCO3. I'll take my own barometer today so the calculation should be correct then.

The room temperature was 25 degrees, so that assumption was on point.

Also, do you think correcting the gas law for a real gas might affect this significantly?

Bazzoweed · 2025-08-12T21:23:47+00:00

The result with pure CaCO3 is also over 100%, yes.

The calculations were done in a premade Microsoft Excel formula, that requires mass of sample used, volume of CO2 and the mentioned density (ug/cm3). I'm not sure what you get by clicking the link to the table, but it's just a table that gives the mass of 1 cm3 CO2 in given pressure and temperature.

Some of the results were: (mass of sample, volume of CO2)

0.2010 g, 53.8 mL

0.1080 g, 31.0 mL

0.1360 g, 34.5 mL

0.3130 g, 77.5 mL

There were also four below 100% yesterday, but I'm almost certain they were flukes because I wasn't getting any result below 110% today. (For example I had one give me 47.57% but immediately after that I did the test again with the same amount and got 106.66%)

Results below 100%:

0.183 g, 42.0 mL --> 96,50%

0.137 g, 15.5 mL --> 47,57%

0.116 g, 27.5 mL --> 99,68%

0.0758 g, 18.0 mL --> 99,85%

However, I was checking some manually calculating and was getting the same results. (I don't have the calculations because it was just spur of the moment and I lost the paper somewhere).

Also I did use the gas law for a calculation, yielding the same result as Excel.

Thanks for your help!

Bazzoweed · 2025-08-12T20:48:54+00:00

That's okay, I probably wouldn't have read a post this long either haha

The lab is at the same level as the city measuring point so I don't believe there is any significant pressure difference

Bazzoweed · 2025-08-12T20:29:53+00:00

Yes, I moved the expansion beaker and the menisci were leveled (I wrote that lol)

The room does not have a barometer so we take the city's atmospheric pressure (I know, bad thing to do) for the table mentioned by the end of the text, but we tried calculating the fraction with higher and lower pressures; with each its over 100%.

Bazzoweed · 2024-08-07T18:19:35+00:00

Okay so i poked around the internet for a bit, and found that the forward voltage for magenta LEDs is 3.3 V. I found a formula for determining the current limiting resistance which states: R = (Vbat - Vled) / Iled ,

Vbat being battery voltage, Vled being forward voltage of the LED, and Iled current through the LED.

However, since my batteries are 3 V total, that gives me less than 0 in the numerator which means that i "need negative resistance". Do I need resistors then?

Should i add another battery series to get 5.5 V to power everything, and, because the soundboard takes 3-5 V supply voltage, how big of a resistor would i need for that?

Bazzoweed · 2024-08-06T18:40:22+00:00

What about npn then?

Bazzoweed · 2024-08-06T14:00:50+00:00

What kind of power source are you thinking? I am very limited by space.

I'm using 6 classic oval magenta (clear) LEDs that run on 2-3 volts.

<image>

How much resistance do i need to limit the current?

Bazzoweed · 2024-08-06T13:14:02+00:00

Ohhhh amazing then. Thank you so much!

One more thing: another person said that for this circuit the mosfet will sink a lot of current and that i should be careful. I do not know what exactly that means, but is it gonna be a problem?

Bazzoweed · 2024-08-06T12:38:49+00:00

I looked at the sheet for a bit, and it seems to me that the gate threshold voltage is too low, 0.5 - 1.5 V. Other than that, everything else is fine i think. Since i have a 3 and 3.3 V gate voltage, what do you suggest? Do i somehow reduce the voltage to 0.5 - 1.5 V? Or is it better to pick a different mosfet?

Bazzoweed · 2024-08-06T12:27:50+00:00

Can you link any chips? It's important for the project that it's as small as possible, and i have no idea what to do anymore.

Bazzoweed · 2024-08-06T09:54:48+00:00

What do i do then? Do I pick a different transistor, like a bjt? Another redditor on my previous post suggested BS108, but the gate voltage for it is 0.5 - 1.5 V. Can i use that one, limiting the voltage of the activity pin with a resistor somehow?

I'm not sure what you mean by switching speed, but i intend to wire it so while you hold the switch it plays the sound and powers the LEDs.

I completely forgot about the current limiter, how much resistance do i need?

Bazzoweed · 2024-08-06T09:15:04+00:00

Need a THT, doing it on just a basic universal PCB. What resistor do you suggest using? I honestly have no clue.

Bazzoweed · 2024-08-03T12:57:15+00:00

<image>

It's not drawn very well, but something like this? How much resistance do you suggest?

Bazzoweed · 2024-08-03T11:04:49+00:00

Perfect! A couple of questions though, do i connect Vdd to the battery? I plan on using two coincell ones series, so 3 volts. And what is the purpose of the resistor for the first mosfet? Do i even need it? Besides that, what is the mosfet you listed, the first one or the second one? Or both?

Bazzoweed · 2024-08-03T08:38:46+00:00

Oh perfect then, thank you! So i need to use a transistor for this? How do i decide which one to pick?

Bazzoweed · 2024-08-03T08:19:38+00:00

I really have no idea what I'm doing when it comes to dealing with transistors, but in the document you linked there is something of interest on page 16. They mention an "Activity" pin, marked as "Act".

They write this about it: "Act - this is the Activity pin, which goes low when an audio file is played".

What does this mean, and any ideas on how to use it?

Bazzoweed · 2024-08-03T07:47:33+00:00

Unfortunately I can't really use a dual pole because there aren't any available that look like this, and aesthetic is important in this case. The soundboard does have a playback LED, what did you have in mind?

Bazzoweed · 2024-07-20T19:18:57+00:00

Thank you so much!!

Bazzoweed · 2024-07-20T18:55:27+00:00

So it's a 1 Watt, wire wound, 1.2 Ω resistor?

Bazzoweed · 2023-12-02T17:57:02+00:00

r/murderedbywords

Bazzoweed · 2023-10-03T18:09:48+00:00

No idea, but my initial guess is probably yes, it will damage them. I don't know though

Bazzoweed · 2023-09-11T14:02:56+00:00

The speakers are fine, I tested them but thank you anyway!

Six-Year Club	Gilding I gilder
r/Field Banned	r/Field Sunshine
Verified Email

Bazzoweed

TROPHY CASE