Page:The American Cyclopædia (1879) Volume X.djvu/255

 LEAD 249 the limit of manifestly deleterious action would seem to be somewhere between one tenth and one twentieth of a grain. An interesting case is reported of the lead disease attacking a large number of the household of the ex-royal fam- ily of France in 1848, while they resided at Claremont, Surrey, England. The spring that supplied the palace had been selected for the purity of its water, and lead pipes had been laid 30 years previously to the palace, two miles distant. Four members of the family manifested some symptoms of poisoning after five months' use of the water, and in seven months 13 persons were alarmingly affected. The water on examination was found to con- tain one grain of lead per gallon. In experi- ments on the effect of Dantzic water on lead pipes, Dr. Lissauer found that the maximum amount of lead was present after one week's use. After the third week there was still a small amount, while after four weeks and during the six months succeeding the water was free from lead. He found further, that when the water contained 3 -8 grains of car- bonate of lime to the gallon the water was without effect on lead. In contact with a less oxidizable metal, lead is more readily attacked than when alone. Lead pipe is consequently found to be more corroded in the vicinity of the soldered joints than elsewhere. A notable quantity of lead has been found by Dr. Hayes in water contained in metallic ice pitchers where the sides were soldered to the bottom. A safe substitute for lead pipe for water sup- ply has been found in the tin-lined lead pipe or lead-encased tin pipe. Careful investiga- tion has shown that these pipes when properly made and jointed effectually resist corrosion by ordinary potable waters, although the wa- ters of some springs and wells have been known to attack tin. As it is not probable that the use of lead pipe will be soon abandoned in cities, it is important to understand how it may be used with the least risk. The greater danger is in general to be apprehended the longer the water is allowed to stand in it before using, and the more the pipes are exposed to the alternate ac- tion of air and water as they are filled and emptied. Pipes in the upper parts of buildings are frequently left empty of water by this being drawn off below, and for this reason are more exposed to chemical action than those constantly filled. The first flow of water through any lead pipes that have been left some time without use will wash out the dis- solved salts of lead. If this water is allowed to run waste to the amount of several times the contents of the pipes, that which follows is not likely to contain any injurious quantity of lead. By thus drawing off every morning the water that has stood in the pipes, and then washing them out by the continued flow for a short time, all risk of lead poisoning may be avoided. The published information on the subject of lead poisoning and the effects of water upon lead is scattered through a vast number of medical and chemical works and re- ports of sanitary committees. The most im- portant works to consult are Ohristison on poisons, and L. Tanquerel des Planches on lead diseases, translated from the French by Dr. Samuel L. Dana (Lowell, 1848). Convenient reference may be had to the opinions of a great number of chemists in the " Collection of Reports (condensed)," prepared and pub- lished in 1859 by Mr. James P. Kirk wood, en- gineer of the Brooklyn water works ; also to the "Report of the Metropolitan Board of Health" (New York, 1869), and an article by Prof. William Ripley Nichols on the action of Cochituate water upon lead pipes, in the " Sec- ond Annual Report of the Massachusetts State Board of Health " (1871). Appended to this latter article is a list of books and monographs on the subject. Ores of Lead. Lead has been found in a few instances native, but such oc- currences are extremely rare. The principal ore of lead is the sulphide or galena. When pure it consists of 86-6 per cent, of lead and 13 -4 of sulphur. It crystallizes in the isometric system, the prevailing form being the cube ; and it has a perfect cubic cleavage. Hardness 2-5 to 2-75; specific gravity 7'25 to 7'7; lus- tre metallic ; color and streak pure lead gray. Heated in an open tube, it gives fumes of sul- phurous acid ; before the blowpipe on charcoal it fuses, emits sulphurous fumes, coats the coal yellow, and yields a globule of metallic lead. It is soluble in nitric acid. It occasionally contains, as impurities, antimony, arsenic, cop- per, zinc, and cadmium. All galena is more or less argentiferous, and also probably aurife- rous, but the physical characters give no indi- cation of the amount of silver present. Gen- erally galena occurring in true veins in the older rocks contains more silver than that oc- curring in deposits in the more recent forma- tions. The following list shows the amount of silver in galenas from a few localities : Hartz Sala, Sweden ... England Lead hills, Scotland Monroe, Conn Roxburv, Conn Eaton, N. H Shelburne, N. H Missouri Arkansas Middletown. Conn Pike's Peak, Colorado. Antimonial galena from Tus- cany Peru, undressed ore, but ex- ceptionally rich Percentage of silver. 0-03 to 0-05 0-05 to 0-75 0-02 to 0-03 0-03 to 0-06 3-00 1-85 0-1 0-15 0-0012 to 0-0027 0-03 to 0-05 0-15 to 0-06 0-05 to 0-06 0-325 to 0-72 0-52 to 3-20 Iqual to troy ounces in a ton of 2,240 Ibs. 9-8 to 16-3 10-3 to 245 6-5 to 9-8 9-8 to 19 6 980 E44 32-7 49-0 0-4 to 0-9 9-8tol6'3 49-0 to 65-0 16 8 to 19-6 106 to 235 170 to 1138 According to E. J. Chapman, galena is seldom highly argentiferous except when associated with mispickel or other arsenical ore. As- sociated with galena, and generally resulting from its decomposition, are frequently found oxidized compounds of lead, as the carbonate,