650 851. Elimination of Mercury, 650, 651 852. Tests for Mercury, 651, 652 853. The Detection of Mercury in Organic Substances and Fluids, 652-654 854. Estimation of Mercury--The Dry Method, 654 855. Volumetric Processes for the Estimation of Mercury, 654, 655 III. PRECIPITATED BY HYDRIC SULPHIDE FROM A NEUTRAL SOLUTION. ZINC--NICKEL--COBALT. 1. _Zinc._ 856. Properties of Metallic Zinc, 655, 656 857. Carbonate of Zinc, 656 858. Oxide of Zinc, 656 859. Sulphide of Zinc--Sulphate of Zinc, 656 860. Preparation and Uses of Chloride of Zinc, 656, 657 861. Zinc in the Arts--Zinc Chromate--Zinc Pigments--Action of Fluids on Zinc Vessels, 657, 658 862. Effects of Zinc, as shown by Experiments on Animals, 658 863. Effects of Zinc Compounds on Man--Zinc Oxide, 658, 659 864. Sulphate of Zinc, 659 865. Zinc Chloride, 659, 660 866. _Post-mortem_ Appearances--Illustrated by Specimens in Pathological Museums, 660, 661 867. Detection of Zinc in Organic Liquids or Solids, 661, 662 868. Identification of Zinc Sulphide, 662 2. _Nickel--Cobalt._ 869. Experiments of Anderson Stuart on the Toxic Action of Nickel and Cobalt, 662, 663 870. Symptoms witnessed in various Classes of Animals after taking Doses of Nickel or Cobalt, 663, 664 871. Effects on the Circulation and Nervous System, 664 872. Action on Striped Muscle, 664 873. Separation of Nickel or Cobalt from the Organic Matters or Tissues, 664, 665 874. Estimation of Cobalt or Nickel, 665 IV. PRECIPITATED BY AMMONIUM SULPHIDE. IRON--CHROMIUM--THALLIUM--ALUMINIUM--URANIUM. 1. _Iron._