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New indicators
348
CURRENT
TOPICS.
[J. F. I.
1.2 times the fat, the calculated value tended to be higher, rather than lower, than the value obtained by analysis. The citric acid content of 27 samples of cream obtained from a separator ranged between 0.9 and 0.19 per cent. with an average of 0.13 per cent., while the citric acid content of 26 samples of mixed farm cream ranged1 between 0.10 and 0.20 per cent. with an average of 0.15 per cent. No evidence was obtained of a seasonal variation in the citric acid content of cream. J. S. H. New Indicators .-BARNETT COHEN, of the Hygienic Laboratory, U. S. Public Health Service (Public Health Reports, 1926, 41, 3051-3074)) describes six new compounds of the sulphonephthalein series which are of value as indicators in volumetric analysis and as reagents for the calorimetric determination of hydrogen-ion concenThe new compounds have the following scientific names, tration. proposed common names, useful pH range, and color change in passing from acid to alkaline : Tetrabrommetacresolsulphonephthalein (brom cresol green), 3.8 to 5.4, yellow to blue; Tetrachlormetacresolsulphonephthalein (chlor cresol green), 4.0 to 5.6, yellow to blut ; Dibromphenolsulphonephthalein (brom phenol red), 5.2 to 6.8, yellow to red ; Dichlorphenolsulphonephthalein (chlor phenol red), 4.8 to 6.4, yellow to red1 ; Dibromdichlorphenolsulphonephthalein (brom-chlor phenol blue), 3.0 to 4.6, yellow to blue ; Metacresolsulphonephthalein (metacresol purple) with a dual pH range and color change, i.e., 1.2 to 2.8, red to yellow, and 7.4 to 9.0, yellow to purple. J. S. H. Faught Test for Acetone.In this test, the unknown solution is mixed with an aqueous solution of sodium nitroprusside. Then several drops of an aqueous solution of ethylene diamine hydrate are added as an upper layer. If acetone be present, a pink or red zone forms at the line of contact. The solution of sodium nitroprusside HARRY J. SCHAEFFF;R, of the Philadelphia must be freshly prepared. College of Pharmacy and Science (Am. Jour. Pharmacy, 1926, 98, 643-645), has studied the relative sensitivity of the various tests for He finds that the Faught test is the most efficient and acetone. delicate, and is of extreme value when small quantities of acetone are He reports the delicacy of the various tests for to be detected. acetone as follows : Dibenzalacetone I : 500, Lieben I : 1000, Kolthoff J. S. H. I : 2500, Legal I : 10,000, Faught I : IOO,OOO. Professional Engineers. More Than 3000 in United States Civil Service.-The United! States Civil Service Commission has just issued an interesting pamphlet which describes the work of engineers There are more than 3000 in the Federal executive civil service. civilian professional engineers in the Government’s employ. Federal engineering operations are carried on in practically every part of the United States, and extend to Alaska, Guam, Hawaii,
CURRENT
TOPICS.
[J. F. I.
1.2 times the fat, the calculated value tended to be higher, rather than lower, than the value obtained by analysis. The citric acid content of 27 samples of cream obtained from a separator ranged between 0.9 and 0.19 per cent. with an average of 0.13 per cent., while the citric acid content of 26 samples of mixed farm cream ranged1 between 0.10 and 0.20 per cent. with an average of 0.15 per cent. No evidence was obtained of a seasonal variation in the citric acid content of cream. J. S. H. New Indicators .-BARNETT COHEN, of the Hygienic Laboratory, U. S. Public Health Service (Public Health Reports, 1926, 41, 3051-3074)) describes six new compounds of the sulphonephthalein series which are of value as indicators in volumetric analysis and as reagents for the calorimetric determination of hydrogen-ion concenThe new compounds have the following scientific names, tration. proposed common names, useful pH range, and color change in passing from acid to alkaline : Tetrabrommetacresolsulphonephthalein (brom cresol green), 3.8 to 5.4, yellow to blue; Tetrachlormetacresolsulphonephthalein (chlor cresol green), 4.0 to 5.6, yellow to blut ; Dibromphenolsulphonephthalein (brom phenol red), 5.2 to 6.8, yellow to red ; Dichlorphenolsulphonephthalein (chlor phenol red), 4.8 to 6.4, yellow to red1 ; Dibromdichlorphenolsulphonephthalein (brom-chlor phenol blue), 3.0 to 4.6, yellow to blue ; Metacresolsulphonephthalein (metacresol purple) with a dual pH range and color change, i.e., 1.2 to 2.8, red to yellow, and 7.4 to 9.0, yellow to purple. J. S. H. Faught Test for Acetone.In this test, the unknown solution is mixed with an aqueous solution of sodium nitroprusside. Then several drops of an aqueous solution of ethylene diamine hydrate are added as an upper layer. If acetone be present, a pink or red zone forms at the line of contact. The solution of sodium nitroprusside HARRY J. SCHAEFFF;R, of the Philadelphia must be freshly prepared. College of Pharmacy and Science (Am. Jour. Pharmacy, 1926, 98, 643-645), has studied the relative sensitivity of the various tests for He finds that the Faught test is the most efficient and acetone. delicate, and is of extreme value when small quantities of acetone are He reports the delicacy of the various tests for to be detected. acetone as follows : Dibenzalacetone I : 500, Lieben I : 1000, Kolthoff J. S. H. I : 2500, Legal I : 10,000, Faught I : IOO,OOO. Professional Engineers. More Than 3000 in United States Civil Service.-The United! States Civil Service Commission has just issued an interesting pamphlet which describes the work of engineers There are more than 3000 in the Federal executive civil service. civilian professional engineers in the Government’s employ. Federal engineering operations are carried on in practically every part of the United States, and extend to Alaska, Guam, Hawaii,