32 Mode of Conducting Chemical Examinations. [January, 
first undergone a very stridt practical examination in Analy- 
tical Chemistry, both qualitative and quantitative, and in 
microscopic work in relation to the detection both of organic 
and inorganic poisons. 
One example will be sufficient to show the necessity for 
the candidates who are selected, or who offer themselves for 
the position of chemical expert, undergoing or being sub- 
mitted to a practical examination such as I have indicated. 
The tests for some of the organic poisons are colour tests , 
— that is, they are distinguished by the colour they give with 
certain reagents ; therefore those who undertake the che- 
mical examination for poison cases ought to be free from all 
colour blindness. Now I have found, in teaching Analytical 
Chemistry during many years, that a not inconsiderable 
number of the students I had to teach — and I have no 
doubt other teachers have found it to be the case with some 
of those they taught — were colour blind; they could not 
distinguish or see the violet colour potassium compounds 
impart to a gas flame, even when the colour was made more 
perceptible by cutting off, by absorption, other colour rays 
by viewing the flame through a glass stained blue with 
cobalt. This violet colour and the yellow colour sodium 
compounds impart to the gas flame were the chief ones the 
majority of the students had to distinguish : whether some 
of the students who were not defective in vision as regards 
the violet colour, and whether some of those who were, 
were colour-blind as regards other colours I am unable to 
say, as inorganic analytical chemistry does not afford a 
means of testing accurately the sight as regards other 
colours. But one case, a very extraordinary one, came 
under my notice. A gentleman, a medical man, came to 
study chemistry with me, and during the time he was with 
me he wished to go through a course of analysis for the 
detection of organic poisons. I found out early, after he 
commenced this course, that he would — on account of his 
defective sight as regards colours — be unable to acquire 
accuracy in this branch of chemical analysis, for he was 
colour-blind as regards most of the colours. 
If it could be ascertained, I venture to say that it would 
be found that our Government authorities have never ascer- 
tained, before allowing an analyst to adt as a chemical 
expert, whether he was free from colour-blindness ; yet in 
this one particular alone my readers will see how important 
it is that those who are appointed to discharge the duties 
devolving upon a chemical expert in poison cases should be 
free from even this one defedt. 
