Dissolving collagen in water: Why does the weighing scale reading fall? Every day I take 10g of hydrolysed collagen dissolved in about 200ml of water.

First I put the cup of water on my digital scale (which measures in 0.1g increments) then I add exactly 10g of collagen and stir it with a spoon until it dissolves.

As the collagen dissolves, the total weight always gradually decreases by about 1.5g - 2g in total. If the total weight of the cup, spoon and water is 300g, when I add the collagen, it becomes 310g, then as it dissolves over the next 15 seconds it decreases to about 308g. All I've done is stir it.

I can't see how this is due to evaporation since I can leave the pure water on the scale for 5 minutes beforehand and the weight doesn't change; but as soon as I stir the collagen in it always decreases.

What's happening?
Because collagen does not react with water and you say, no (measurable) evaporation of water is evident, there are only two options as to what is happening:


Matter is converted into energy:
If virtually no evaporation or spillage took place, and your scale is working properly, this is what must have happened. Using the formula of mass-energy equivalence $E=mc^2$ (E = energy, m = mass, c = speed of light in a vacuum) we can calculate the amount of energy that should result from a "loss" of 2 grams:
$$ E = 0.002~kg\cdot(2.998\cdot10^8~m/s)^2 $$
$$ E = 0.002~kg\cdot8.988\cdot10^{16}~m^2/s^2 $$
$$ E = 1.798\cdot10^{14} (kg~m^2)/s^2 = 1.798\cdot10^{14}~J$$
so... that would be a LOT of energy.
Your scale is not working as intended.


I'd go with option 2.

Now on a serious note: We do have a scale (precision of 0.0001 g) in our lab that occasionally has the same problems. Sometimes I would measure an empty reaction flask and it would be fine but some other time I could watch the measured weight drop by the second, "losing" up to 100 mg. The scale was checked by a professional but he could not find anything wrong with it.

My advice is: try another scale, see if the problem persists.