Numb

We all know about sodium chloride, common table salt, NaCl (Na because sodium has been known for so long that its symbol derives from its Latin name 'natrium'). Add an atom of oxygen to the compound and it becomes NaOCl, sodium hypochlorite, a different beast altogether: explosive in its pure, solid form; a strong, corrosive alkali in solution; highly reactive, an oxygenator, damaging to living cells. Somewhat unstable even in solution, it decomposes to release chlorine, giving it a distinctive smell - if it is mixed with an acid, such as vinegar, it reacts to produce significant amounts of chlorine, potentially quite dangerous.

It is, of course, the principle active ingredient of household bleach - used for generations as a general disinfectant, cleanser and bleaching agent. Slightly unnerving then, when my dentist - providing a commentary on his actions while dealing with my root canals this afternoon, to fill the absence of conversation - mentioned that he was going to swill them out with sodium hypochlorite, before filling them with little pegs that look like the ones used for keeping score in cribbage. The contrast between this Victorian remedy and the other high-tech wizardry involved in the process would have made me smile, except that... well, you know

I recognised the smell though - not just from the kitchen cupboard, school chemistry or the swimming pool, but because smell is a portal to memory and, combined with the formal chemical name, I was taken back to the family dairy farm of my childhood, and the drums of concentrated hypochlorite that were delivered for us to dilute, and then use for cleansing of milking equipment, pipes and glass collecting jars

At that time it was my grandfather's farm. He was wounded in the second battle of the Somme. Like most veterans of that bloody war, he did not talk about it, but he could only sleep with the aid of drugs, both prescribed and self-administered. I don't know if he ever encountered chemical warfare; if he did, it was quite likely to have been chlorine gas. It had never occurred to me before today that something as simple as washing up after milking might have carried him back to the mud and the blood and the wire

Our scattering of snow was sparse compared to many places. I know it's inconvenient and cold and muddy, but I'm still charmed by snow - another resonance of childhood magic, perhaps. It will not be here for long, and I'll be worrying about dried-out barrel timbers leaking water soon enough, toothache long forgotten