TRANSACTIONS OF SECTION B. 727 



antimony in 1,600,000 parts of solution may be thus detected. The precipitation 

 of small quantities is complete in one hour. 



Mefciiry is separated from a nitric acid solution as metal, on a small closely- 

 wound platinum spiral. A current of 4-5 c.c. per minute can be used. As a 

 confirmatory test the spiral is washed, dropped into a test-tube, heated to sublime 

 the mercury, and then converted into the iodide by the addition of a small crystal 

 of iodine and warming gently : 0-0001 grm. of metal can be detected thus in 

 l.jO c.c. of solution. 



Lead is precipitated either as peroxide at the anode from a nitric-acid solution 

 or as metal from an ammonium-oxalate solution ; the latter method is more deli- 

 cate, but the former has the advantage that it can be made approximately quanti- 

 tative. In this case also 0-0001 grm. is readily detected, the confirmation being 

 •effected by converting the metal or oxide into the sulphide or iodide. 



Copper is electrolysed as usual from an acidified solution, and 0-00005 grm. 

 can be readily detected, the confirmation being effected by dissolving the precipi- 

 tated metal in acid and testing with potassium ferrocyanide. Quantitative results 

 with 1 mgrm. of metal are obtained thus. 



Cadmium is best deposited from a potassium cyanide solution, with a current of 

 €-2 c.c. per minute. The yellow sulphide serves as the confirmatory test : 

 0-0001 grm. of metal can be thus detected. 



The detection of the above metallic poisons in urine can be effected directly by 

 these methods as described, but owing to the presence of the organic matter it is 

 necessary to pass the cui-rent twice as long as when aqueous solutions are employed. 

 In twenty-four hours a current of 1-2 c.c. per minute completely decomposes urine, 

 leaving a clear solution. In the case of lead the electrolysis of an ammonium- 

 oxalate solution gives a more delicate reaction than the separation as peroxide from 

 nitric acid solution. To detect these poisons in other cases the destruction of the 

 organic material with which they are associated, by the ordinary means, is 

 necessary. 



These electrolytic tests are one and a half time more delicate than the colori- 

 metric tests for antimony and copper by means of sulphm-etted hydrogen, and ten 

 times more delicate than the tests for mercury and lead by the same reagent. 



It is further to be noted that the methods are in many cases methods of separa- 

 tion as well as of detection, e.g., the separation of lead from iron by electrolysis in 

 nitric acid solution. Also where it is desirable to obtaui approximately quantita- 

 tive results, electrolysis possesses a marked advantage over the usual colorimetric 

 processes, because the erroneous results due to the influence of the varying con- 

 stituents in the solutions tested on the reliability of the reaction are entirely 

 obviated. 



3. Interim Report on the Proximate Constituents of Coal. 



The Committee desired reappointment, as their investigations are not yet 

 completed. 



4. Apparatus for Extraction for Analysis of Oases Dissolved in Water. 

 J5y Edgar B. 'Truman, Jf.D., F.C.S., Borough Analyst, Nottingham. 



A glass flask of 500 c.c. capacity is joined by means of its tubular termina- 

 tion to a second lower flask of 200 c.c. capacity by means of a water-joint. 

 In the lower flask is suspended from the upper one a thermometer, reading up to 

 150° C. From the neck of the upper flask proceed two millimetre tubes. The 

 right-hand one, after receiving a stopcock, expands into a cup having a 

 capacity of .30 c.c. The tube on the left rises to the level of the bottom of the 

 cup. This tube has two tubes supplied with stopcocks joined on to it at right 

 angles — one above and the other below. To the one above is attached, by a 

 water or glycerine joint, a mercury tube doubled on itself above and below, 

 and having a length when so doubled of 880 mm. This tube is graduated in 

 mm. from to 400 in two directions, downwards in the open limb and upwards 



