The synthesis was published here on APUG many years ago. Use Potassium Sulfite, Hydroquinone and Hydrogen Peroxide. The more concentrated the Peroxide the more concentrated the HQMSK will be at the end. As you go up in concentration, the reaction becomes very vigorous and generates a lot of heat so beware.
On the subject of HQMS synthesis I found parts of two interesting relevant papers. Sadly, only an "abstract" is available, the rest is behind a paywall. The first is a
1951 paper by James E. LuValle and the second a
1985 paper by James P. Youngblood, both employed by Kodak when these papers were published. So, the mechanism of synthesis is roughly this:
Under the right pH conditions, hydroquinone reacts with oxygen (peroxide) and forms p-benzoquinone. This seems to produce some more hydrogen peroxide as a byproduct.
P-benzoquinone reacts with a sulfite salt and gives the equivalent hydroquinone monosulfonate salt, plus some metal hydroxide. If sodium sulfite was used, then HQMS-Na salt and NaOH will be produced.
Sulfite present during these reactions can also be further oxidised to sulfate.
So, it seems that the key reaction is the one converting HQ to p-benzoquinone, but I'm not entirely sure that simply mixing HQ, peroxide and sulfite will convert 100% of HQ to HQMS. Apart from that, we still don't know the quantities of sulfite and hydroxide present at the end, which probably makes it even more problematic (I assume sulfate can be just disregarded). Perhaps a better way would be to synthesize pure p-benzoquinone first and react it with the right amount of sulfite, but this is quite a nasty chemical substance.
P-benzoquinone can be produced by reacting HQ with peroxide, but usually an iodide catalyst should be present, if good yields are desired. The catalyst could be I
2, or an iodide salt like KI, but given that iodide is a powerful restrainer, any impurities at the final product can cause problems.