Role of Potassium Dichromate in Prime

[cmjlab]

Just curious if anyone knows what role Potassium Dichromate plays in primes for difficult to ignite stars (ex. One of the Crackle Prime and Veline's Star Prime have dichromate).

 

I've read a couple theories based on dichromate as a possible catalyst for perchlorate to ease ignition. Does that mean it reduces the ignition temp of the perchlorate, or is it something else?

 

Just curious if anyone knows, I've used dichromate for very little other than treating magnesium, strobe comps, and priming Crackle. For the life of me, I can never get consistent ignition of Crackle as stand alone stars in a shell, but once I started using a high silicon prime with dichromate in it, they began consistently igniting.

 

Again, just curious, thanks.

 

Chuck

[redbullzuiper]

I guess you are referring to the veline prime?

Lloyd knows the guy, so he can probaly awnser it what the real reason behind it was.

Regardless, there are two theories why it might have been added.

1. As a catalyst

2. To preven reactions between nitrate / magnalium

As for the first one, I do not think this was the main reason, but rather the second. Most burst powders are made from black powder, so my guess is that its added to create some sort of buffer between the composition and the burst powder. In regards to the nitrate / magnesium reaction.

Ive never bothered to add the dichromate. I dont see the value of it, as a bind my stars alcohol based anyway.

But as I stated, lloyd probaly knows the real reasoning behind it, as he knows the guy, but I bet it has to do with the second theory

[Zumber]

The prime that uses potassium perchlorate and organic fuels ,potassium dichromate acts as a burn catalyst it aids potassium perchlorate to decompose there by reducing activating energy.

One of most important characteristics of good prime is that it should be ignited readily and generate abundant thermal energy.

If prime itself not easily ignited then stars tends to blow blind more.

[AustralianPyromaniac]

As others have said it is a very effective catalyst for perchlorate decomposition. Good primes of course must be ignited easily and engulf the star nearly instantly. There are a few chemicals that can be used, but dichromate aiding perchlorate decomp has been studied and used a lot. The inclusion of only a 4-5% percent potassium dichromate increases the burn rate of perchlorate comps by more than 50% as quoted in Shimizu. Without a catalyst, the reaction occurs in stages as each oxygen is lost forming the two "stable" intermediates KClO3 and KClO, with a catalyst the reaction occurs smoothly and at a lower temperature, improving the performance and consistency of the prime.

For metal protection, the dichromate forms a passivating coat on the surface of the particles, this reaction occurs relatively slowly even in a concentrated solution of dichromate. I do not think adding dichromate to a comp as a powder would do anything for that issue.