Black Mass

Patches of conductive lead sulphide can be formed on lead in the presence of sewage. This can result in the flow of a large corrosion current . Sulphate-reducing bacteria in soils can produce metal sulphides and H2S, which results in the formation of deep pits containing a black mass of lead sulphide . Other micro-organisms may also be involved in the corrosion of lead in soil . 

FIGURE 15.17 Sulfuric acid is a dehydrating agent. When concentrated sulfuric acid is poured on to sucrose (a), the sucrose, a carbohydrate, is dehydrated (b), leaving a frothy black mass of carbon (c). 

Rust formed by atmospheric corrosion is often voluminous (Fig. 18.4) and visually appears as loose orange-brown or black masses. This type of rust is always a mixture of phases and frequently consists of two layers - magnetite at the iron/rust interface (as a result of reduced oxygen supply) with an outer layer of loose lepidocrocite and/ or goethite. Hematite is formed during high temperature aqueous corrosion and is also found in the passive layer (which forms at room temperature). 

Dimethyl selenide, (CH3)2Se.—An intimate mixture of selenium and amorphous phosphorus (5 2) is heated, and the black mass powdered and heated in a retort with concentrated sodium hydroxide and potassium methyl sulphate. The mixture foams and a yellow liquid distils over. This is separated from the water and fractionated to remove dimethyl diselenide, which is present in small quantity. 

The potassium cyanide is first melted in a porcelain crucible at 650° in the absence of air, and poured out on a marble slab. It is then remelted in a clay or porcelain crucible, and the dry, finely-powdered element added in portions, the mixture being agitated from time to time, and jhe heating continued for fifteen minutes after the final addition. The cooled black mass is placed in warm water, and the insoluble residue of nitride and amorphous carbon is carefully and gently ignited in air to remove the carbon. 

Ni Catalyst from Ni Formate (byAllisson et al.)45 In this method 100 g of nickel formate with 100 g of paraffin and 20 g of paraffin oil are heated in a vacuum of water-stream pump. At 170-180°C the water of crystallization is evolved out first (in 1 h). About 4 h at 245-255°C is required for complete decomposition. The end of the decomposition can best be found by the pressure drop to 20 mmHg. The still hot mass is poured on a plate after solidification, the upper paraffin layer is removed as much as possible. The remaining deep black mass is washed with hot water until most of the paraffin is removed off with melt the remaining powder is washed with alcohol, and then many times with petroleum ether until no paraffin remains. 

According to Chesneau,6 a polysulphide, Co2S7, is precipitated as a black mass when a solution of sulphur in aqueous sodium monosulphide is added to one of cobalt chloride. If this precipitate is dissolved in sodium polysulphide solution and the liquid evaporated in vacuo, black crystalline plates separate out. 

Nitro-cobalt, Co2(N02), is obtained as a black mass when nitrogen peroxide suitably diluted with nitrogen is passed over reduced cobalt.4 Water decomposes it vigorously, cobalt nitrate with very little nitrite is produced, together sometimes with a basic salt. When heated in nitrogen it evolves nitrous fumes, then decomposes -with almost explosive violence, leaving a mixture of cobalt and its oxide. 

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