09:06 – Costco run and dinner with Mary and Paul yesterday. I’d forgotten what a zoo Costco is on Saturdays. We usually go on Sundays, when it’s much less busy, but Paul and Mary are devoting today to Super Bowlish stuff.
Today we’ll assemble 11 more chemistry kits, which is all we have components for. I also need to put together purchase orders for more components, both for the chemistry kits and for the first 60 biology kits.
As we were riding to Costco yesterday, I was telling Paul about how I’d been screwed again by research. I was making up 0.5% aqueous eosin Y stain for the biology kits. I weighed out 5.00 g of eosin Y powder and dissolved it in about 900 mL of distilled water. The result was an intensely colored deep red solution, so dense that when I held it up to the fluorescent tube on the ceiling I couldn’t see light through the bottle. Alas, I’d been doing some research and came across a couple of papers from about 1924 that mentioned that making the stain 1% with respect to acetic acid made the resulting stain much more effective, staining cell components a much deeper red.
So I added 10 mL of glacial acetic acid, whereupon the contents of the flask turned a flocculent bright orange. Hmmm. I had to allow the contents of the flask to settle for several days to be certain, but it turns out that a significant amount of the eosin Y had precipitated as flakes. Crap. Just to be sure, I used a drop of that solution on a specimen. Rather than staining cell components a deeper red, it stained them a very, very pale orange.
My first inclination was to locate the grave site of that paper’s author, dig him up, and drive a stake through his heart. In all fairness, though, I’m willing to admit that he almost certainly merely reported what he observed. The eosin Y I bought in late 2011 may well have been very different from the stuff he bought under the name of eosin Y in 1924. Stains are notoriously variable in composition, even now. I think I’ll titrate some of my orange mess with sodium hydroxide. I’m betting that it’ll turn a nice intense red and the flakes will go back into solution as the pH increases.
13:00 – We just finished building 12 more chemistry kits, so we now have 13 in stock. Now I need to go through inventory and figure out what components I need to order for 60 more chemistry kits and 60 biology kits.
That takes care of discrete components, but the other issue I’ve done nothing about so far is raw materials inventory. That is, the kits, both chemistry and biology, contain numerous bottles of chemicals. Some of those are solids, which are easy to calculate. If a kit contains a 25 gram bottle of a particular solid chemical, I know that I need 1.5 kilograms of that chemical to build 60 kits. Allowing for some wastage, that means I need to have two kilograms or four pounds in stock, on order, or in combination.
Solutions are more complicated. For example, the biology kits will contain a 30 mL bottle of Benedict’s reagent. For 60 kits, I need 1,800 mL nominally, so I’d make up 2 liters. Two liters of Benedict’s solution requires 200 g of anhydrous sodium carbonate, 346 g of sodium citrate dihydrate, and 34.6 g of copper(II) sulfate pentahydrate, so that’s three separate raw materials to keep track of. And many of the chemicals used in various solutions are used in more than one of the solutions, so there’s not necessarily a one-to-one mapping between a kit solution and the chemicals that make it up.