swiip read this in erowid : ( http://www.erowid.org/archive/rhodium/chemistry/meth.hi-p.html )

PROCEDURE 2

In a 500 mls round-bottom flask is added 150 mls of glacial acetic acid, 15 grams of red phosphorus, and 33.50 grams of iodine.[NOTE 6] The mixture is allowed to react for 15 - 20 minutes, until all of the iodine has reacted. Then add 10 mls of distilled water and mix, then add 8.07 grams (0.04 mole) of EPHEDRINE HCl, and mix. A reflux condenser is added to the 500 mls round-bottom flask and the mixture is gently refluxed (gently boiled continuously) for 2 and 1/2 hours. The hot mixture is suction filtered while still hot to remove the excess red phosphorus.[NOTE 7] The hot filtrate is added slowly by pouring into a solution of 20 grams of sodium bisulphite in 1 liter of distilled water. The solution is made basic and solvent extracted as above using two 100 ml portions of ether, washed and dry.[NOTE 4] The oily residue extracted (after removing the ether) is a mixture of methamphetamine, iodo-ephedrine and minor amount of acetic ester ephedrine.[NOTE 5]

swip found this pdf in org syn about reduction with RP/I  and  glacial acetic acid.
swip wonder if is true that with 2 1/2 hours of reflux  you make it , because  swip always think you need 24 hours at least , swip utfse and dont find other refernce about glacial acetic acid and RP/I and the speed of the reaction (24 h to 2 1/2)

 

swiip read this in erowid : ( http://www.erowid.org/archive/rhodium/chemistry/meth.hi-p.html )

PROCEDURE 2

In a 500 mls round-bottom flask is added 150 mls of glacial acetic acid, 15 grams of red phosphorus, and 33.50 grams of iodine.[NOTE 6] The mixture is allowed to react for 15 - 20 minutes, until all of the iodine has reacted. Then add 10 mls of distilled water and mix, then add 8.07 grams (0.04 mole) of EPHEDRINE HCl, and mix. A reflux condenser is added to the 500 mls round-bottom flask and the mixture is gently refluxed (gently boiled continuously) for 2 and 1/2 hours. The hot mixture is suction filtered while still hot to remove the excess red phosphorus.[NOTE 7] The hot filtrate is added slowly by pouring into a solution of 20 grams of sodium bisulphite in 1 liter of distilled water. The solution is made basic and solvent extracted as above using two 100 ml portions of ether, washed and dry.[NOTE 4] The oily residue extracted (after removing the ether) is a mixture of methamphetamine, iodo-ephedrine and minor amount of acetic ester ephedrine.[NOTE 5]

swip found this pdf in org syn about reduction with RP/I  and  glacial acetic acid.
swip wonder if is true that with 2 1/2 hours of reflux  you make it , because  swip always think you need 24 hours at least , swip utfse and dont find other refernce about glacial acetic acid and RP/I and the speed of the reaction (24 h to 2 1/2)

2 P + 3 I2 ==> 2 PI3
2 PI3 + 6 H2O ==> 2 H3PO3 + 6 HI
============================
2 P + 3 I2 + 6 H2O ==> 2 H3PO3 + 6 HI
============================


I posted this back when The Hive was online and novices were looking for a fast reduction. The key to the mechanics is the ratio of 0.04 mole of EPHEDRINE HCl, to very large HI excess, which drives the reduction rate faster to the right. The glacial acetic acid acts as an ionic solvent.


Reaction rate. http://en.wikipedia.org/wiki/Reaction_rate

Factors influencing rate of reaction.

The nature of the reaction: Some reactions are naturally faster than others. The number of reacting species, their physical state (the particles that form solids move much more slowly than those of gases or those in solution), the complexity of the reaction and other factors can influence greatly the rate of a reaction.
Concentration: Reaction rate increases with concentration, as described by the rate law and explained by collision theory. As reactant concentration increases, the frequency of collision increases.
Pressure: The rate of gaseous reactions increases with pressure, which is, in fact, equivalent to an increase in concentration of the gas. For condensed-phase reactions, the pressure dependence is weak.
Order: The order of the reaction controls how the reactant concentration (or pressure) affects reaction rate.
Temperature: Usually conducting a reaction at a higher temperature delivers more energy into the system and increases the reaction rate by causing more collisions between particles, as explained by collision theory. However, the main reason that temperature increases the rate of reaction is that more of the colliding particles will have the necessary activation energy resulting in more successful collisions (when bonds are formed between reactants). The influence of temperature is described by the Arrhenius equation. As a rule of thumb, reaction rates for many reactions double for every 10 degrees Celsius increase in temperature,[2] though the effect of temperature may be very much larger or smaller than this.
For example, coal burns in a fireplace in the presence of oxygen but it doesn't when it is stored at room temperature. The reaction is spontaneous at low and high temperatures but at room temperature its rate is so slow that it is negligible. The increase in temperature, as created by a match, allows the reaction to start and then it heats itself, because it is exothermic. That is valid for many other fuels, such as methane, butane, hydrogen...

Reaction rates can be independent of temperature (no-Arrhenius) or decrease with increasing temperature (anti-Arrhenius). Reactions without an activation barrier (e.g. some radical reactions), tend to have anti Arrhenius temperature dependence: the rate constant decreases with increasing temperature.

Solvent: Many reactions take place in solution and the properties of the solvent affect the reaction rate. The ionic strength also has an effect on reaction rate.
Electromagnetic Radiation and Intensity of light: Electromagnetic radiation is a form of energy. As such, it may speed up the rate or even make a reaction spontaneous as it provides the particles of the reactants with more energy. This energy is in one way or another stored in the reacting particles (it may break bonds, promote molecules to electronically or vibrationally excited states...) creating intermediate species that react easily. As the intensity of light increases, the particles absorb more energy and hence the rate of reaction increases.
For example when methane reacts with chlorine in the dark, the reaction rate is very slow. It can be sped up when the mixture is put under diffused light. In bright sunlight, the reaction is explosive.

A catalyst: The presence of a catalyst increases the reaction rate (in both the forward and reverse reactions) by providing an alternative pathway with a lower activation energy.
For example, platinum catalyzes the combustion of hydrogen with oxygen at room temperature.

Isotopes: The kinetic isotope effect consists in a different reaction rate for the same molecule if it has different isotopes, usually hydrogen isotopes, because of the mass difference between hydrogen and deuterium.
Surface Area: In reactions on surfaces, which take place for example during heterogeneous catalysis, the rate of reaction increases as the surface area does. That is due to the fact that more particles of the solid are exposed and can be hit by reactant molecules.
Stirring: Stirring can have a strong effect on the rate of reaction for heterogeneous reactions.

All the factors that affect a reaction rate, except for concentration and reaction order, are taken into account in the rate equation of the reaction.