Mumbles Posted August 2, 2014 Posted August 2, 2014 The talk of using alcohol solutions or alcohol to wet compositions and BP has got me thinking. I was actually trying to find data on dextrin solubility in alcohol solution, but that has been more difficult to find. Instead I turned my attention toward nitrate solulubility in alcohol solution. The idea being if using an alcohol solution could limit finely milled nitrate from redissolving. As you can see in the chart, you knock the solubility down to about half to a third of that in pure water in some of the more commonly used alcohol concentrations (20-30%), and would dissolve about 3g out of 75g in 100g of BP. It would still probably activate dextrin, though is generally more than I'd recommend. It comes from A. Ralph Thompson and M. C. Molstead; Ind. Eng. Chem., 1945, 37 (12), pp 1244–1248.
Bobosan Posted August 2, 2014 Posted August 2, 2014 Mumbles, of the different types of isopropanol listed, where would denatured be?....if at all? Can you correlate the "i" numbers with an alcohol type?
Mumbles Posted August 2, 2014 Author Posted August 2, 2014 Denatured isn't listed. I'll see if I can find one for ethanol as well though. Denatured alcohol is ethanol with different additives to make it unfit for human consumption, and thus not subject to alcohol taxes. The use of different additives by different companies will make any real figures difficult to measure and brand specific. Isopropanol, while sometimes added to ethanol to denature it, is chemically different. You might be more familiar with it being called rubbing alcohol. Potassium nitrate will be more soluble in ethanol than isopropanol. The "I" number is just alcohol concentration. I-7 is 93% water and 7% alcohol, and so on. As a side note, some of the tables only go up to 40-50 degrees. This is because above these temperatures the solution separates into two phases.
Bobosan Posted August 2, 2014 Posted August 2, 2014 I've read other differences between the two are denatured is a primary alcohol with 2 carbon atoms while the isopropanol is a secondary with 3 carbon. Could this difference have any bearing on BP chemical performance?
gregh Posted August 2, 2014 Posted August 2, 2014 You are correct, it is the secondary isomer of propanol where the OH would be attached to the end of the molecule. Isopropyl is 2 propanol, with the OH affixed to the 2nd or center carbon. This bends the molecule and makes it highly polarized.
AzoMittle Posted August 3, 2014 Posted August 3, 2014 Awesome! I was looking for something like this myself! I was thinking about the burn-rate curve of rockets and how to neutralize (flatten) it. Once you move past things like grain geometry it seems the best way for a solid propellant is to cast a grain within a grain. It is a concentric circle shape, or a bullseye-target shape. That is the core of the rocket would run on a faster burning fuel and the outer fuel would be retarded so that as burning area increases the the Isp of the fuel decreases. The problem with this is that you can only get so many discrete fuel stages. In a 1# rocket you may be limited to only two stages, as diameter increases it becomes easier to add another stage. I want to do it without discrete stages, I want a pure gradient. What I have been experimenting with lately is finding a way to saturate either a retardant (such as sodium bicarbonate) or a catalyst (such as iron oxide) into the cast grain. The first and foremost problem is finding a solvent/solution that will slowly carry the modifier into the fuel grain without breaking down the fuel. The secondary problem is that you then have to drive off the solvent/carrier-fluid so as that you are left with a dry and operational fuel grain.
Niladmirari Posted August 3, 2014 Posted August 3, 2014 My 2 cents. Solubility in ethanol alcohol solutions. Lower (second) table.
ChrisDeHont Posted August 3, 2014 Posted August 3, 2014 He is my two cents about this seeing I have a lot to do with this alcohol and BP theory... After I shot the show last night I had time to reflect with one of my technicians about this... He has a PhD is chemistry and offered this advice. Dextrin has absolutely no solubility in alcohol. We all know this. But, with out looking at it by 100X here is what may be happening. It has to do with the charcoal and KNO3. He THINKS that the KNO3 is being incorporated at a molecular level with the charcoal.. Effectively making it one compound, thus causing the burn rate of the BP to be extremely fast. We all think of the BP being mixed in a mill to incorporate all the chemicals into a SINGLE compound, even tho with all the milling in the world, the KNO3, Charcoal and S will never be truly one. Only an extremely fine mixture. The alcohol may change this as we think. At least from his point of view.. By mixing alcohol with at least the KNO3 and Charcoal, he believes that one of the compounds, most likely the KNO3 is being fully dissolved into the charcoal. Thus resulting in only two of the chemicals being mixed into the final BP. Like I stated in previous post, I will be testing this theory extensively cause has of right now I have homemade BP that is stronger than any commercial or other homemade batches(that I made). I would like to et this formula down to repeat this over and over.. The money to be saved.
Recommended Posts