tcrial was measured in September 1960 and again in March 1961. The two spectra are identical, neither giving a hint of contamination with porphyrin nor “free chlorin.” Positive identification must remain in doubt until further study. 9. (Page 258, last paragraph.) The
black waxy pigment, insoluble in glacial acetic acid, has a very simple spectrum. Its blue-green solution in benzene may be so dilute that the weaker bands do not show up. It is not the intention of the report to say that this pigment is identical to pheophytin 8, But with what can it be compared, if not with pheophytin a?
LITERATURE CITED
(1) LUCM,John, Orten J. M., J. Biol. Chon. 191, 293 (1951). (2) Fischer, H;, Stern A., (‘Die Chernie des PYrroh VOl. 11, Part 2, Fig. 7 , p. 342, Akadernische yerlagsgesellschaft,
Leipzig.
W. WARRENHOWE
Colorado School of Mines Golden, Colo.
Qualitative Determination of Mercurous Ions with Potassium Antimono-Ta rtrate C. A mixture of the cations listed in section A was similarly tested and a black precipitate was observed. In the absence of mercurous ions, the test gave a white precipitate. The presence of mercurous ions resulted in a black precipitate also when sodium hydroxide or ammonium hydroxide were used, and a bright mirror when EXPERIMENTAL pyridine was used. When pyridine or A. A 2% aqueous solution of potasammonium hydroxide were used, the sium antimono-tartrate was prepared Au+3 solution did not turn red-purple. and 1% aqueous solutions of the folD. Potassium antimono-tartrate was lowing cations: Ag+, Al+31 Asf3, added to a very dilute solution of Au+3. Ba+2. Bi+3. Cat2. Cd+2. C O + ~ . mercuric ions and the mixture was Cu+2; Fe+a; Hgz42, K4, Li+,’ R.lgf2; made alkaline with pyridine. No black Mn+2, Na+, NHa+, Ni+2, Pb+2, Sn+‘, precipitate was observed. Sr+2, Th+‘, Ti+S.U02+2.and Zn+2. B.’ To 1 ml.’of each of the above RESULTS AND DISCUSSION solutions of cations was added 1 ml. of the potassium antimono-tartrate soluThe above facts indicate that the tion. Dilute potassium hydroxide was black precipitate is due to the presence added immediately to each misture of mercurous ions. On analysis this until it was alkaline. A black preprecipitate was found to be metallic cipitate appeared in the solution conmercury, and this indicates that the taining mercurous ions; the other reaction described in (1) was actually solutions either remained clear or white the reduction of mercuric ion to meror light yellow precipitates were obcurous ion and then to metallic merserved. The Au+3 solution became a cury. If pyridine is used as a base, it is deep red-purple.
SIR: The qualitative detection of mercuric ions with potassium antimonotartrate has been reported recently (1). Further information has indicated the possibility of the qualitative detection of mercurous ions as well.
possible to distinguish mercuric from mercurous ions, since the former are not sufficiently reduced in dilute solutions. Iodine interferes due to its reduction to iodide (8). We also found that bromine undergoes a similar reaction. Chromates and dichromates interfere since they form strongly colored basic salts. In the presence of strong oxidizing agents the reaction was inhibited, but the addition of cupric nitrate allows the reaction to proceed. The red-purple solution of Au+’ ions as formed in section B was highly staining on the human skin. This is a hydrosol of gold and this method appears to be a convenient way of preparing it. LITERATURE CITED
(1) Chinoporos, Efthimios, ANAL.CHEM.
32,1364 (1960). (2) Hale, F., J. Am. Chem. SOC.24, 828 (1902). EFTHIMIOS CHINOPOROS NICHOLAS PAPATHANASOPOULOS
Suffolk University Boston. Mass.
A Simple Recorder of Ultraviolet Absorption in Column Effluents G. S. Begg, St. Vincent’s School of Medicdl Reseaxh, Melbourne, N. 6, Australia SIMPLE
and inexpensive unit for re-
A cording ultraviolet absorption in chromatography effluents allows the operator to follow directly the events during an elution and thus to modify the operation of the column-e.g., by introducing a gradient, a t the proper time. This does not require that the recording be quantitative, and consequent,ly the design can be rather simple. However, the unit can be modified to give a quantitative response, 12%
ANALYTICAL CHEMISTRY
if desired. The wave length used is the 2537-A. mercury line, a t which a very large numler af compounds show appreciable absorption. Our own interests have chiefly been :n proteins and phenylthiohydantoins. PRINCIPLE OF OPERATION
Light from a low pressure mercury lamp passes through a quartz flow cell containing the effluent and strikes Em ultraviolet-excitable fluorescent ma-
terial. The secondary, visible light output is then measured by a photoconductive cell. The same principle had been used earlier by P. Edman and J. Sjaquist [Acta Chem. Scand. 10, 1507 (1956)l for the visual assessment of paper chromatograms. Special precautions have to be taken in two respects. First, the visible output from the mercury lamp has to be prevented from reaching the photoconductive cell. For this purpose a fluorescent material with a secondary
