This may seem trivial, but I would advice borrowing some of the chemical from other lab and trying to do it again. I had a case when my newly purchased potassium diphosphate behaved the same way (did not dissolve well and contained suspended particles) and it turned out to be of bad quality.

Yes, I agree with Natella. One thing you can try is to mix up a batch at 1M and check again for particles. If you still have them, it's probably contamination. For a very sensitive way to check for particles, use a laser pointer. Just shine the beam through the solution and try to observe light scattering at right angles. Use a darkened room for this so your eyes have good sensitivity. If you can find a green laser, that would be best because the eye is most sensitive to green.

Another thing you can try is to re0crystallize the CaCl2. Before the availability of high purity reagents, in-lab re-purification was a very typical first step in chemistry.

I hope this helps!

Hello, I checked the solubility of CaCl2 and it is 45 wt% at 298K but of course the solubility is strongly dependent on temperature. I don't think 75 wt% can be reached within a reasonable temperature concentration (i.e. it is "only" 62 wt% at 100oC).

Another important parameter is the hydration of the initial salt. Except for Na+ and K+, it is very rare to have initially anhydrous chlorides. They mostly have a formula of the type CaCl2.nH2O (I think n might be equal to 6 for CaCl2 but you need to check with the provider). This means that the amount of water in the initial salt has to be corrected to get the right concentration.

If you send me a message via this website, I can provide you with the stability diagram of CaCl2.

The CaCl2 I am using is anhydrous one from Sigma (C1016). It is mentioned in the product catalogue that a clear and colorless solution will be obtained for the 10% (W/V) concentrated solution but we couldn't obtain a clear solution at all even for a less concentration.