Metallic arsenic, heated in a glass tube closed at one end, yields a black sublimate of a metallic lustre, and at the same time gives out the characteristic alliaceous odor. This is the case too with alloys of arsenic, if there is a maximum quantity of arsenic present. When heated in a glass tube open at both ends, metallic arsenic is oxidized to arsenious acid, which appears as a white crystalline sublimate on the sides of the glass tube. This deposit will occur at some distance from the assay, in consequence of the great volatility of the arsenic. The sublimate can be driven from one place upon the tube to another, by a very low heat. Alloys of arsenic are converted into basic arseniates of metal oxides, while surplus arsenic is converted into arsenious acid, which sublimes on the tube. If too much arsenic is used for this experiment, a dark-brown incrustation will sublime upon the sides of the tube which will give an alliaceous smell. If this sublimate should be deposited near the assay, then it resembles the white sublimate of arsenious acid. Heated upon charcoal, metallic arsenic is volatilized before it melts, and incrusts the charcoal in the flame of oxidation as a white deposit of arsenious acid. This sublimate appears sometimes of a greyish color, and takes place at some distance from the assay. When heated slightly with the blowpipe flame, this sublimate is instantly driven away, and being heated rapidly in the reduction flame, it disappears with a light blue tinge, while the usual alliaceous or garlic smell may be discerned. Arsenious acid sublimes in both glass tubes very readily, as a white crystalline sublimate. These crystals appear to be regular octahedrons when observed under the microscope. Upon charcoal it instantly volatilizes, and when heated, the characteristic garlic smell may be observed. Arsenic acid yields, heated strongly in a glass tube closed at one end, oxygen and arsenious acid, the latter of which sublimes in the cool portions of the tube. Compounds of arsenic produce, in consequence of their volatility, no reactions with fluxes. Being heated upon charcoal with carbonate of soda, they are reduced to metallic arsenic which may be detected by the alliaceous odor peculiar to all the arsenic compounds when volatilized. NINTH GROUP.--COPPER, SILVER, GOLD. These metals are not volatile, neither are their oxides. They are reduced to the metallic state, by fusion with carbonate of soda, when they melt to a metallic grain. The oxides of silver and gold are reduced _per se_ to the metallic state by ignition. In the reduction of the oxides of this group, no sublimate is visible upon the charcoal.