Day: May 12, 2015

Tuesday, 12 May 2015

08:09 – I turn 62 years old next month. Barbara asked me last night if I intended to apply for Social Security. I told her that would be crazy. I’ll wait at least until 66, when I’m eligible for full benefits, and probably until age 70. If I applied now, I’d get literally nothing because the government would deduct $1 from my monthly check for every $2 I had in outside income above $15,720.

Not that I ever intend to depend on Social Security. It won’t surprise me if I end up getting nothing at all. By the time I reach full retirement age of 66 four years from now, I expect they’ll be applying earnings limits even for those of us who are eligible for full benefits. If I do get something, I’ll consider it a supplement that can disappear at any time.


11:57 – I’m filling bottles and making up solutions. I just made up 4 liters of 1 molar sodium carbonate, and as always I’m struck by how very complex something apparently as simple as a solid dissolving in water can be. There are kinetic and thermodynamic issues any time you put a solid into solution. Most solids are both more soluble and faster-dissolving in warm water than cold, but there are exceptions in both cases. And, although it seems intuitive that a very soluble solid should dissolve faster than a sparingly-soluble solid, that’s far from being true. Some very soluble solids (on both a grams/liter and moles/liter basis) take a long, long time to dissolve, while some much less soluble solids dissolve much faster.

Sodium carbonate is one of those odd solids in that it exhibits retrograde solubility. Maximum solubility occurs at 35.4 C, just under body temperature. At higher and lower temperatures, solubility is lower. But speed of dissolution increases with increasing temperature, so sodium carbonate dissolves faster in hot water, even though its solubility is lower.

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