FISHER SCIENTIFIC CO

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REPORT

The Fisher Titrimeter® is a good scout. Five ways.

A Fisher Titrimeter is trustworthy. It takes the guesswork out of titrations. You can count on it to give you accurate, reproducible endpoints every time. A Fisher Titrimeter is loyal. The Automatic Model works virtually alone—no breaks, no time off. It frees you and your technicians for more important work. A Fisher Titrimeter is helpful. There are models that can take over your potentiometric titrations . . . visual titrations . . . micro titrations . . . Karl Fischer titrations. A Fisher Titrimeter is obedient. Once you've shown it the correct endpoint, it will return to it unerringly time after time after time. A Fisher Titrimeter is thrifty. Every model will save you valuable time. The Manual Model has an especially attractive price, an attractive design. This isthe Fisher "good scout" law: to provide you with reliable, versatile trtrators that in these five ways—and many o t h e r s will do you a really good turn daily. Write for product literature. Fisher Scientific Co., 1004 Fisher Building, Pittsburgh, Pa. 15219. Or call your representative for more details. Be a good SCOUt, tOO. We have taken liberties

with the Scout Law. But the Fisher

Titrimeter

obeys it

INSTRUMENT DIVISION FISHER SCIENTIFIC CO.

J-741 faithfully.

exposed to relatively large surface areas of the containers during the processing of the sample. Contamination problems will be less for the AAS methods that are inherently simpler than the chemical methods. Reagent-grade acids contain traces of metals, some of which originate from the glass bottles used for storage. Although the concentration of each of the metals present is specified to be below the 1 ppm level (8), the acids used must be included in a study of reagent blanks. This source of contamination may be significant, as in the dissolution of 1 g of a sample that requires 15 ml of acid. For example, a contaminating metal when present at the 1 ppm level in the acid (sp. g. 1.3) will contribute a blank (20 /xg) equivalent to 20 ppm in the 1-g sample. Conclusions from the Comparison oj the Methods. To summarize what I have said thus far, it is necessary to compare atomic absorption with the well established chemical methods being replaced to understand the rapid growth of AAS. In retrospect we should not be surprised to learn that the standard chemical methods could be supplanted so rapidly by a method that has some of the advantages of an ideal method: (1) Specificity. (2) Low limit of detection for many elements, which is important in trace analysis and in working with dilute solutions to minimize interferences. (3) The determination of several elements in one sample solution. (4) The determination of many elements with one instrument. (5) Freedom from the elapsed time requirements of those chemical methods in which reactions must go to completion, as in color development and the drying of precipitates. (6) Provision for data output in direct readout form. The enthusiasm for AAS is remarkable in that it does not stem from

Circle No. 55 on Readers' Service Card 34 A

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ANALYTICAL CHEMISTRY