I've been searching the Hive files & Rhodium's page for info on how to convert Sodium Hypophosphite to Hypophosphorous Acid. What I found is that almost all of the good Hive posts on the subject are missing. Because SWIM doesn't have a major stash of lab glass anymore, he/she decided to "wing it" and try this...
Add 50 mL of 32% HCl to a beaker
With magnetic stirring, add 50g NaH2PO2*H20 (Sodium Hypophosphite) in portions
Using a fan blowing over surface of solution, evaporate over low heat to 1/2 original volume
Filter NaCl precipitate
Dilute with dH2O to achieve proper concentration
Questions: What ratio of Sodium Hypophosphite:32% HCl should be used?
What concentration of Hypophosphorous Acid does this ratio produce?
How far does the post-reaction Hypophosphorous Acid solution need to be evaporated for filter NaCl precipitate?
SWIM is well aware of the fact that this may be completely wrong. He/she is doing the best that he/she can with the information available.
To a stirred solution of 717.8 g of a 32% hydrochloric acid solution in a 3-necked 2 liter flask was added 615.42 g of powdered sodium hypophosphite. The temperature of the solution rose about 2° C. Water was removed from the stirred reaction mixture by reduced pressure distillation at a temperature of about 55°C ±7° C at a pressure of 44-72 mmHg until a hypophosphorous acid concentration of about 80 wt% was obtained. After cooling to room temperature, sodium chloride that had precipitated was filtered from the reaction mixture. The filter cake was washed twice with 32 wt % hydrochloric acid.
The recovered product contained 355.7 g of hypophosphorous acid. The analysis showed that the product contained 0.9 wt% sodium, 3.2 wt% chloride, and 80.96 wt% hypophosphorus acid. Chloride ion was removed from hypophosphorous acid using an ion-exchange column (height 221/4", diameter 11/8"). The column was packed with Rohm and Haas Resin IRA-410 in the chloride form and was regenerated using 5% NaOH.
SWIM doesn't have the glassware to evaporate under vacuum or remove the Chloride ion using an ion-exchange column, so advice was taken from the Hive file:
readyeddie (Hive Bee) wrote:
You want to evaporate the solution to salt with very little heat.Then all you have to do is add 1 ml of concentrated hydrochloric acid to 1 gram of the hypo salt.
More Questions: Is it required to remove the NaCl to use the hypo for HI reductions?
Is it required to remove the remaining Chloride ions?
Any other suggestions?
What are the recommended ratio's when using only Sodium Hypophosphite for creation and regeneration of HI?
Pseudo:I:Hypophosphite:H2O(mL) ratio would be helpful.
What would be the ballpark reaction time if the reaction was done this way?
Will the reaction run with any hypophosphite salt?
Has this method been tested?
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