In the August 16, 2012 issue of my hometown paper, The Fulton County News, there

Question

In the August 16, 2012 issue of my hometown paper, The Fulton County News, there was a report of a resident who was charged with the poisoning of her husband by adding Visine drops to his drinking water. Reportedly, her husband had a blood level of 49 ng/mL tetrahydrozoline hydrochloride (C13H16N2 HCI), the active ingredient in Visine. To what molar concentration does this correspond? If the male human body has roughly 4.7 L of blood, what is the total mass of tetrahydrozoline believed to be in his blood? Assuming that she delivered the dosage in a single 8 oz serving of water, how many drops of Visine, which is 0.05 % tetrahydrozoline hydrochloride (by weight), did she add? (Assume that 1 drop is roughly 0.05 mL and that the density of the solution is roughly 1 g/ml_.)

Explanation / Answer

Solution :-

Concentration is 49 ng/ml

There fore 4.7 L * 1000 ml / 1 L = 4700 ml

4700 ml * 49 ng / 1 ml = 230300 ng in 4.7 L blood

Lets convert ng to gram

230300 ng * 1 g / 1*10^9 ng = 0.00023 g

Now lets calculate the moles

Moles of C13H16N2.HCl = 0.00023 g / 236.7405 g per mol = 9.728*10^-7 mol

Now lets calculate the concentration

Molarity = moles / liter

             = 9.728*10^-7 mol / 4.7 L

             = 2.07*10^-7 M

Total mass in the blood = 230300 ng

That is 0.0002303 g

Now lets calculate the drops

8 oz * 29.57 ml / 1 oz = 237 ml water

0.0002303 g * 100 % / 0.05 % = 0.4606 g

0.4606 g / 0.05 ml = 9.212 drops

9.212 drops of visine

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