------------------------------------------------+---------------------- | Parts by Weight. Calomel, and Corrosive Sublimate. +-----------+---------- | Chlorine. | Mercury. ------------------------------------------------+-----------+---------- Calomel, or proto-chloride of mercury | 36 | 200 Corrosive sublimate, or bi-chloride of mercury | 72 | 200 ------------------------------------------------+-----------+---------- Hence the ratio of chlorine in these two chlorides is as one to two. Botanists have long used a solution of corrosive sublimate in alcohol, known by the name of Smith’s solution, to preserve the specimens in their herbaria from the aggressions of insects. The Rev. J. Wood, writes:[34] “I know to my cost sundry Kaffir articles being absolutely riddled with the burrows of these tiny beetles (_Anobium striatum_), and not to be handled without pouring out a shower of yellow dust, caused by the ravages of the larva. The most complete wreck which they made was that of a New Guinea bow, which was channelled from end to end by them, and in many places they had left scarcely anything but a very thin shell of wood. “In such cases I have but one remedy, viz. injecting into the holes spirits of wine in which corrosive sublimate has been dissolved. This is not so tedious a business as it may seem to be, as the spirit will often find its way from one hole to another, so that if half a dozen holes be judiciously selected, the poison will penetrate the whole piece of wood, kill all the insect inhabitants, and render it for ever impervious to their attack. The above-mentioned bow cost me but little trouble. I first shook out the greater part of the yellow powder, and then, placing the bow perpendicularly, injected the spirit into several holes at the upper end. The effect was magical. The little beetles came out of the holes in all directions, and not one survived the touch of the poisoned spirit; many of them, indeed, dying before they could force themselves completely out of the holes. The ticking of the deathwatch is, in fact, the call of the _anobium_ to its mate, and as the insect is always found in old woods, it is very evident why the deathwatch is always heard in old houses. There is, by the way, a species of cockroach which acts in a similar manner, and generally disports itself on board ship, where the sailors know it by the name of ‘Drummer.’” The earliest account[35] we can find of the use of corrosive sublimate to destroy worms in woods is a few words mentioned, in 1705, by M. Homberg, French Academian. In that year he stated that a person of position in Provence, France, knew how to make a parquet floor which would resist the worm, viz. by soaking the wood in water in which corrosive sublimate had been mixed, and this process he had always found to be very successful.