NEWS chromatography. According to J. B. Himes and L. D. Metcalfe, Armour & Co., traditional methods of ion ex change and paper chromatography are accurate but slow (2 to 3 days) when a large number of samples is involved. In their method the apparatus used is a small, sealed stainless steel pan containing a stainless steel rack with a glass trough and six glass rods. The solvent system consists of methyl ethyl ketone, propionic acid, and water (15:5:6) held at 60° C. The amino acid spots are developed with ninhydrin and absorbance of the spots read with a densitometer. By use of this horizontal paper chro matography at 60° C , the developing solvents move more rapidly. The amino acid composition of a mixture of 18 amino acid hydrochlorides or a protein hydrolyzate can be determined quan titatively in two hours. This system, the authors state, is very rapid, less tedious, and reasonably accurate. Nonaqueous Titrations. Tetrabutylammonium hydroxide has proved to be an improved quaternary ammo nium hydroxide titrant for the quanti tative determination of strong acids or inorganic salts in nonaqueous solutions, reported R. H. Cundiff and P. C. Markunas, R. J. Reynolds Tobacco Co. Until recently, the authors stated, nonaqueous titration methods have been limited primarily to the analysis of amine salts and salts of alkali and alkaline earth metals. Using 0.1ΛΤ tetrabutylammonium hy droxide, they have carried out differ entiating titrations of several acid mixtures in pyridine solution. Acid mixtures involved include sulfuric and nitric, hydrochloric, perchloric phos phoric and sulfonic, respectively. They have also applied the reagent success fully in resolving a mixture of a strong, weak, and very weak acid. They have also conducted research on nonaqueous titration of inorganic salts of strong acids and strong bases. Salts of all types, including nitratenitrite mixtures, can be determined titrimetrically by this technique if the compound will undergo an anion ex change reaction with the acidifying agent. The method involves acidifica tion of the salt with an excess of strong acid (sulfuric), addition of a non aqueous solvent which precipitates the cation as the sulfate, and a differentiat ing potentiometric titration with the reagent, tetrabutylammonium hydrox ide which reacts with the liberated acid and excess sulfuric acid not reacting with the cationic portion of the salt. Salts of strong acids and weak organic bases can be titrated directly with the reagent without first being acidified.
Analyzing for Sodium? Calcium? Potassium? Here's how to do it accurately quickly, easily
These typical industrial analyses, accomplished with a Coleman Flame Photometer, demonstrate a speed and precision impossible by classical methods: 1. Sodium, Potassium and Calcium in Soils— 10,000 samples per year in an industrial Chem ical Company laboratory. 2. Potash in fertilizers—96 samples per day, in a State agriculture laboratory. 3. Calcium Oxide in magnesite, brucite and dolo mite ores—120 to 140 ore samples per 8-hour shift, in a mining company laboratory. 4. Sodium and Potassium in such diverse materials as silicate rocks, plant tissues, bentonite clays, food-stuffs and lubricating oils. Find out how a Coleman Flame Photometer can save time and money in your laboratory—write for Bulletin B-242.
The Coleman Flame Photometer COLEMAN
INSTRUMENTS, INC.,
DEPT. A ,
MAYWOOD,
ILLINOIS
For further information, circle number 45 A on Readers' Service Card, page 101 A
VOL.
30, NO. 10, OCTOBER 1958
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45 A
