Reaction of citric acid and calcium chloride I was planning to extract citric acid from lemon juice by reacting the lemon juice with calcium chloride hoping it would react to form calcium citrate and precipitate according to the reaction 
$$\ce{2 C6H8O7(aq) + 3 CaCl2(aq) -&gt; Ca3(C6H5O7)2(s) + 6 HCl(aq)}$$
However I was not sure that the reaction would occur.  I know that the calcium citrate should precipitate out and drive the reaction forward, however it seems that the $\ce{HCl}$ generated reaction would then react with any calcium citrate bringing back to calcium chloride and citric acid.  Which reaction would move to completion or would the two reactions reach an equilibrium.  If this will not work I plan to just use calcium hydroxide instead by reacting calcium chloride with sodium hydroxide.
This procedure is done in our laboratory class, but first you have to add sodium hydroxide until the lemon juice is somewhat alkaline. Then add the calcium chloride (use $1~\mathrm{ml}$ for every $2~\mathrm{ml}$ of the lemon juice + $\ce{NaOH}$ solution).
I think the calcium chloride would first react with the hydroxide, producing calcium hydroxide, which would then react with citric acid to form calcium citrate.

$$\ce{2 C6H8O7 + 3 Ca(OH)2 -&gt; Ca3(C6H5O7)2.4H2O + 2H2O}$$

Filter out the salt (precipitate) formed, weigh it, then you would have to add sulfuric acid afterwards to react with the calcium citrate. This would then form citric acid (soluble) and a precipitate which is calcium sulfate. 

$$\ce{Ca3(C6H5O7)2.4H2O + 3H2SO4 -&gt; 2C6H8O7 + 3CaSO4.2H2O + 2H2O}$$

You would then have to concentrate the filtrate to obtain the citric acid crystals.