292 REVIEWS — Taylor's treatise on poisons. 



boiled with, copper gauze, this is introduced into a tube and laeated, 

 when a ring of araenious acid is formed." The process is undoubt- 

 edly an excellent one where considerable quantities of arsenic are 

 present and in experienced hands, but where tbe reverse condition 

 occurs, the results are often very unsatisfactory. At page 367, Dr. 

 Ta3dor allows that from the experience of Dr. Geobegan it appears 

 that much arsenic is lost, and only one half is re-obtained in a crystal- 

 line form ; this of itself should form an insuperable objection to the 

 sole employment of this method where the amount of poison is small, 

 and more particularly when it is desirable to ascertain its quantity. 

 Moreover, in cases Avhere sulphide of arsenic is present the test is 

 inapplicable, as that compound is insoluble in hydro-chloric acid. It 

 is also well known that various substances interfere with and prevent 

 the reaction, although it is true they are not likely to be present in 

 the case under consideration. 



Dr. Taylor very correctly remarks that " the value of chemical 

 evidence does not depend on the discovery of any particular quantity 

 of poison in the stomach," and also, that " there is a strong preju- 

 dice among lawyers that the chemical evidence is defective, unless 

 the quantity found is sufficient to cause death." The objections 

 often raised in courts of law are unquestionably absurd, but they are 

 raised, and if the chemist can meet them by determining with abso- 

 lute certainty the quantity of poison existing in the viscera, it is his 

 duty to do so, and as the votary of an exact science and in the dis- 

 charge of a most responsible office, he will adopt that process which 

 will enable him to report on this point with perfect accuracy, from 

 the results of his own experiments, from absolute weighings, rather 

 than one in which at the end he is obliged to make a mere estimate 

 or to rely to a great extent on the assertions of others. 



la regard to the quantitative determination, the second process 

 leaves nothing to be desired, a measured portion of the final solution 

 being treated with sulphurous acid, and the arsenic precipitated as 

 sulphide, collected and weighed, or dissolved in ammonia, and the 

 solution evaporated, &c. (The arsenic acid might also be determined 

 as the ammonio-magnesian salt.) The same process is recommended 

 by Dr. Taylor, but without previous destruction of organic matter, and 

 hence the sulphide will scarcely ever be pure. " When we are dealing 

 with the tissues the quantity of arsenic is generally too small for the 

 application of this method, the liver containing only a few grains" ; 



