[Selloum]

Hi,

I'm trying to figure out how the author calculated the 0.069 g of quinine present in his tonic water here:

Quinine Simple Syrup Recipe
INGREDIENTS
615 grams of sugar
615 grams of water
0.5 gram quinine sulfate USP
**these ingredients are given by weight but will produce 1 liter of syrup by volume.

The standard sweetness of tonic water is 10 percent sugar by weight, so a liter of tonic made with our syrup will have 170 ml (208 grams) of quinine simple syrup and therefore 0.069 grams of quinine—much less than the legal limit of .083 grams per liter. Even to approach the limit with this syrup, you’d have to make tonic water that was almost 13 percent sugar by weight, which would be unpalatably sweet.

Tonic water is a mixture of Quinine Simple Syrup and Water.
Knowing from the text that the author wants to make a liter of tonic water and he has 170ml of Q.S.S. for his 10% sugar by weight, we can safely assume that the water added is 830ml.
From his Q.S.S. recipe we know that we can calculate the g/ml of quinine in Q.S.S.
0.5g / 1000 ml = 0.0005g/ml
If I multiply that by 170ml I get 0.085g for the Q.S.S.
How do I calculate the concentration of quinine now that he's added 830ml of water to that 170ml of Q.S.S.?

Thank you

[AWK]

You still need to convert quinine sulfate dihydrate to pure quinine. The term quinine in Wikipedia can help.

[Selloum]

why? I don't see the relevance for this problem.

[chenbeier]

It is relevant because molar mass of quinine sulfate dehydrate is different from  pur quinine.

[Selloum]

I understand that, what I mean is I don't think the author differentiates the two. When he writes quinine he means quinine sulfate dehydrate. So, what I'm asking is what are the calculations to get 0.069g of quinine sulfate dehydrate in his tonic water.

[chenbeier]

No, he separate quinine and the quinine sulfate dihydrate.

Calculate the 0,085 g with molare mass of the disulfate and calculate back you get 0,070 g

https://www.sigmaaldrich.com/catalog/substance/quininesulfate3914720767144111?lang=de&region=DE

[Selloum]

Thanks! That makes more sense. Easier than I thought.