I have a supply of pool chlorinating tabs, and so I am more interested in the reaction between HCl and calcium hypochlorite, than the admittedly
better and well-trodden reaction between HCl and TCCA.
In len1's post on the subject he shows the imperfections in the hypochlorite generation method, and I have a question about his analysis - in "the
hypochlorite reaction" section, he states
Quote:
The results were inferior to the TCCA reaction in almost every respect. Its best to summarise them pointwise.[...]
2. The reagent mixture heated up, requiring cooling to prevent excessive effervescence and run-away.
I observed that upon the reaction running to completion, first on a 0.1M scale then 5M, it never ran away. Actually with my hood on, over the course
of the reaction it dropped a few degrees. It may be because (a) I stirred the reaction as soon as it stopped clumping, and (b) I used -10°C 15% HCl.
I thought I remembered reading something vague about not wanting the reaction temperature to rise above 60°C in this thread. However, after the initial chlorine dissipated, and my blue hypochlorite had turned slightly green, I heated the pot up to 80°C and
observed a lot more gas generation, probably 1.5 times as much. Is this HCl and not chlorine? Is there a practical difference? It seems to form
S2Cl2 just the same.
Perhaps it's my fundamental lack of knowledge that leaves me with this question.mackolol - 2-6-2020 at 00:37
I had the same situation with TCCA chlorine generation. After heating the mixture up several times I got even bigger quantities of chlorine than at
the beginning. I guess it is actual chlorine, because HCl wouldn't evolve from the mixture so easily and as far as I remember it had green colour.
Furthermore, when I added excess of HCl to the mixture, It evolved more chlorine just after addition withoud heating.
It turns out that the bigger HCl concentration is, the faster the reaction goes. And heat also drives the reaction through as without it it dies down
around half.
Maybe it is the matter of prior HCl concentration and speed of the addition. If one adds HCl faster, the more heat is generated and it may even lead
to effervescence, this would be more efficient in terms of chlorine generation, but I don't really know how fast chlorine is absorbed, so I prefer on
slower chlorine generation (sometimes too slow...).
So I think from now on, I will just put hotplate under my chlorine flask and gently heat it as the reaction progresses.
