REVIEWS — Taylor's treatise on poisons. 291 



I I. The solution can now be used in Marsh's test. 



II. The residue has still to go through three operations, all of 

 which are of the simplest kind, viz. : fusion in a porcelain cruci- 

 ble, treating with sulphuric acid until all the nitric acid is evolved, 

 and solution in water. These, as the writer can testify, can all be 

 completed in half, or at most, three-quarters of an hour, and the 

 solution is then ready for Marsh's test. 



It will be seen, therefore, that this incredibly complicated process 

 consists of almost exactly the same number of operations as the one 

 which Dr. Taylor so much prefers, inasmuch as the excess of three in 

 the one mentioned in the last paragraph is counterbalanced by the 

 repeated evaporations with nitric acid in the other. The time required 

 would probably be about the same in both. 



If we next examine into the number of chemicals employed, we find 

 that sulphuric and nitric acids, and alkalic carbonate, are used in both 

 cases, but in the process which is to be rejected on account of the 

 enormous number of chemicals, three more are required, viz. hydro- 

 chloric acid, ammonia, and chlorate of potassa ; the first is used by Dr. 

 Taylor, in Reinsch's test, and must consequently be pure ; the second 

 is recommended by him in the process for the quantitative determina- 

 tion of arsenic (page 368), and must of course be equally pure, and 

 there consequently only remains one extra chemical, chlorate of 

 potassa, which as far as we know never contains arsenic, but be that 

 as it may, the proof of its purity need not form an insurmountable 

 difficulty. 



Danger and Flandin allow that the carbonization process may cause 

 a loss of arsenic, and Heinrich Rose, in his Handbook, distinctly 

 states such to be the case. In the other process none can take place,- 

 as it has been shown by Schacht and others that no arsenic is evolved 

 from its mixture with chlorate of potassa and hydro-chloric acid, unless 

 the temperature be raised above that of boiling water. The arsenical 

 solution finally obtained, is absolutely free from organic matter, which 

 is of great importance, both in Marsh's test, and in the quantitative 

 determination of the sulphide, while in the first process its complete 

 removal depends on the repeated treatings with nitric acid, and this 

 cannot be quite relied on. 



Dr. Taylor recommends Reinsch's process as " applicable to the sepa- 

 ration of arsenic from organic tissues without previous carbonization, 

 the substance being digested with dilute hydrochloric acid, and then 



