Page:Proceedings of the Royal Society of London Vol 60.djvu/371

344 a larger dose, and finally the coagulation of the intravascular blood when the dose is again increased.

Colloid 7 .—The colloid 7 is formed by heating together at 130° C. in sealed tubes, for three hours equal weights of alloxan and metamidobenzoic acid, with twice their weight of phosphorus pentoxide. The product of the reaction is a white powder, very slightly soluble in cold water, and sparing soluble in warm water. It should be washed in ice-cold water till the excess of phosphoric acid is removed, and the remaining substance dissolved in concentrated ammonia. The resulting solution is opalescent and straw-coloured, and should be evaporated down at the temperature of the laboratory in, when a number of translucent, yellowish plates, closely resembling the previously described colloids, are formed. These plates are soluble in warm water, and the solution is pale straw-coloured, opalescent, and lsevorotatory (aD = —41) and shows the following reactions:—

Colloid 7. h n o 3 n h 4 o h. (heating). Millon’s reagent. Frohde’s reaction. CuS04 and KHO. NiS04 and KHO. C0 SO4 and KHO. Salicylsulphonic acid. Yellow solution. Dirty brown ppt. Blue precipitate. Yiolet solution. Very faint yellow solution. Dark brown solution. No precipitate.

It is separated from solution by saturation with either magnesium sulphate, sodium sulphate, sodium chloride, or ammonium sulphate, the colloid rising to the surface of the liquid as a white scum, which redissolves, forming an opalescent solution when thrown into distilled water. It is precipitated by silver nitrate, lead acetate, and mercuric chloride. If the precipitate formed by the addition of lead acetate is suspended in distilled water, and a current of sulphuretted hydrogen is passed through the liquid, the precipitated colloid again passes into solution.

When heated in the presence of a trace of a neutral salt, fractional heat-coagulation is obtained, which will be detailed in a subsequent section.

If the colloid 7 is injected into the circulation of dogs or pigmented rabbits, even in large quantities, it does not produce intravascular coagulation, although it somewhat hastens the coagulability of blood withdrawn from the cai’otid.

The colloid 7, although yielding many of the chemical reactions that have been used as distinctive tests for and also behaving in a very similar manner to the previously colloids, does