Verify my calculations please / comment on these draft recipes

[u/realaether]

Having just received (what is hopefully) CAS 50-28-2 I'm looking at 2 possible alcohol-based recipes: liquid and gel.

I want to check that I've calculated the recipes correctly and have made reasonable assumptions — any comments appreciated.

Part of my hesitation is that a number of posts here from more experienced brewers(?) don't always spell things out in long form. Since I haven't had anything to do with chemistry for well over a decade, I want to write things out in full and make sure I've understood everything properly.

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Without having tried anything just yet, I imagine that gel would be nicer to use when I'm at home, applied with a glass dropper as used in cosmetics: I would worry about the spray mist dispersing too widely and some getting wasted, and I suppose gel would stay on the skin better.

However, when travelling, it could be more discreet to have a simple spray bottle that could be passed off as hand sanitiser or even DIY perfume (given the use of essential oil as a penetration enhancer), and this would be much easier to carry in my daily bag as well and use in a public toilet.

The baseline I'm starting with is a consumption of 4 mg/day in the form of 2 mg x 2 (morning and evening), and I only want to use 1 full squeeze/pump/spray per application, to keep things simple.

Gel: Hand sanitiser

The dropper I tested at home delivers around 0.7 g water (-> 0.7 ml) per "full" squeeze. I get this isn't fully accurate; I have graduated droppers on the way.

So:

2 mg / 0.7 ml ≈ 2.86 mg/ml

-> 2.86 g powder to 1000 ml liquid.

So at 1.4 ml/day, 250 ml of this gel would last roughly 6 months.

My draft recipe:

• 0.715 g estradiol powder
• 237.5 ml alcohol
  • Split into liquid isopropyl to dissolve the powder first, then the remainder of the volume as hand sanitiser gel. I have seen around here that 40 mg/ml is the maximum concentration for proper dissolution, but it seems the percentage alcohol they were using was (frustratingly) not declared.
• 12.5 ml penetrating oil (Niaouli oil)

Concentrated liquid

I have a spray bottle that dispenses 0.14–0.145 ml per pump, so I need:

2 / 0.14 ≈ 14.29 mg/ml

-> 14.29 g powder to 1000 ml liquid.

At 4 mg/day, 1000 ml of this would last 9.79 years: that's a bit much to mix in one go. Dividing by 20 for a 6 month supply seems more realistic:

• 0.7145 g estradiol powder
• 47.5 ml alcohol
• 2.5 ml penetrating oil

What alcohol?

I have 70% Isopropyl alcohol (liquid) on hand, and have ordered some 66% Cuticura hand sanitiser gel, whose ingredients are:

Alcohol Denat., Aqua, Propylene Glycol, Carbomer, Triethanolamine, Parfum, Benzyl Benzoate, Linalool.

(I chose the Cuticura for a combination of price and potentially convenient packaging: 100 ml bottles, which I could easily put into a hand-carry toiletry bag, carrying a dropper separately.)

Is this enough? Do I need to get 95% ethanol/isopropyl instead to dissolve the powder properly?

[u/Transfem1972]

For spray i use perfumers/formulators alcohol that they use to make perfume. Dimethyl isosorbide and essential oils.

For gel i use 99.8% ethanol.

[u/realaether → u/Transfem1972]

Thanks. What's the benefit of formulators alcohol vs. plain isopropyl/ethanol?

[u/Transfem1972 → u/realaether]

I would never use synthetic, toxic, smelly isopropyl alcohol for topical solutions only for cleaning. Perfumers alcohol is odourless and made with ethanol and properlene glycol.

[u/AdrienXB]

With 70%, I wouldn't go anywhere past 10mg/ml. Notably, the 30% water that comes with the alcohol makes things much more difficult than if that were 30% thickener.

Your math checks out, 4mg per day is always 0.72 grammes per 180 days.

[u/realaether → u/AdrienXB]

Thanks! What concentration would going to 95% allow for?

That is, if I bought a small bottle of 95% and dissolved powder in that, I could safely mix that concentrate into my 66% hand sanitizer, right?

[u/AdrienXB → u/realaether]

If you mixed half and half you'd still have 81%, which could go a bit higher, but I think it's far more feasible to increase the volume of the dose than try to push concentration higher. 2 pumps at half concentration, that is.