It was concluded that color-botly formation as a result of aging would have no effect upon infrared analyses, although atmospheric water-pickup can be serious. DISCUSSION
The technique.. described for alkylpj ridines provide useful procedures for analysis of a limited number of samples of widely varying, and unknown, impurity content. Differential niethods are particularly useful for this sort of determination as I\ ell as for trace :tnalyses. Unexpected constituents, whicli absorb exactly a t the chosen analytical band, constitute the greatest hazard in any spectroscopic analysis method. The long-scan technique described for determining 3-picoline in 4-picoline (Table II,D) and charts like Figure 1 can aid the analyst greatly in detecting such situations. The advantages of base line techniques for measuring are many, particularly in the potassium bromide region where water depresses the background transmission severely. The hump-to-hump method of drawing base lines was found superior to choosing fixed n-ave lengths, betn-een which the base line was inexorably draTvn. When it failed, one could suspect such serious interference that any base-line method of correction would be insufficient. Vsing undiluted samples has not affected Beer’s law in the case of the pyridines, providing sufficiently thin cells are used and the concentration range is not too great. The elimination of solvent dilution has the threefold advantage of reducing water absorption through sample handling, reducing sample-preparation time, and eliniinating dilution errors. n7it11 strong absorption bands it might require the use
of very thin cells (
