Medical Jurisprudence And Toxicology

630 MEDICAL JURISPRUDENCE

and then sufficient 10 per cent solution of sodium carbonate or caustic soda
is added to change the. colour of the solution from brown to yellow. On
gently heating on a water bath, a yellow precipitate of lodoform is termed,
which is identified by its characteristic smell and by its hexagonal crystals
seen under the microscope. Besides alcohol, other substances, such as
aldehyde, acetone, amyl alcohol, lactic acid, etc, give the iodoform reaction,
2 Ethyl Acetate Test.— On heating a few drops of the distillate with
0 5 g ' of anhydrous sodium acetate and 1 cc. of concentrated sulphuric acid
in a test tube, the fruity odour of ethyl acetate is noticed, when a dilute
solution of sodium carbonate is poured into the test tube,

3. Ethyl Benzoate Test.— A few cubic centimetres of the distillate are
shaken with a drop or two of benzoyl chloride in a test tube, and then 10
per cent caustic soda solution is added drop by drop until the mixture is
rendered strongly alkaline. On warming, the irritating odour of benzoyl
chloride disappears and the sweet, fruity odour of ethyl benzoate appears.
Methyl alcohol also gives this reaction, but it does not give the iodoform
reaction.

4. Svlphomolybdic Acid Test — If 2 to 3 cubic centimetres of the
distillate are gently poured over 2 cc. of sulphomolybdic acid taken in a test
tube, a deep blue ring appears at once at the junction of the two liquids, If
the tube is shaken, the whole mixture becomes deep blue*

Sulphomolybdic acid is prepared by dissolving by heat 1 g. of molybdic
acid in about 25 cc. of concentrated sulphuric acid.

5. On heating some of the distillate with 5 cc. of a strong aqueous
solution of potassium dichromate and 1 cc, of strong sulphuric acid, the
colour changes to green, and the vapour of aldehyde is detected by its odour,

The following method4 of testing alcohol in blood and urine is favoured by the
panel of the Royal Institute of Chemistry : —

The Cavett Method for Alcohol Estimation. (To be followed exactly,)

Note 1.— It is essential to ensure that the small Erlenmeycr flask and stopper are
•thoroughly cleaned wilh hot chromic acid and rinsed at least six times with tap water
and twice with distilled water. Dry both flask and stopper in an air oven. Grease must
not be used on stoppers— for lubrication merely damp the part of the stopper that fits in
the top of the flask with distilled water and ensure that the water docs not enter the
flask.

Note 2.— As this is a micro method, it is essential to take the special precautions
that are common in such work. The laboratory itself must be clean and free from dust,
and exceptional care in such matters must be taken. It is essential that the distilled
water should be freshly distilled into a clean glass vessel—ordinary laboratory distilled
water is likely to give falsely high results.

Apparatus.— (1) A special 50 ml. Erlenmeyer flask, the glass stopper of which carries
a small cup. (2) A 0.1 ml or 0.2 ml. delivery pipette, for use with urine samples, cali-
brated by each operator to deliver 0.1 ml. (3) A 0.1 ml. Ostald-Folin wash-out pipette,
for use with blood samples, calibrated by each operator to contain 0,1 ml, In uue
these pipettes should be rinsed out with 0.1 ml. of distilled water, which is added to the
blood in the cup. (4) A burette capable of being read to 0,02 ml, which should be
checked by calibration.

Reagents (All reagents must be recognised analytical reagent grade),

1. Potassium Dichromate, standard .solution.— Dissolve 0.4258 g. of potassium dichro-
mate in water and make up to 1 litre ; 1 ml. of this solution is equivalent to 0,1 mg* ol
ethyl alcohol.

2. Sulphuric Acid concentrated.

3. Sulphuric Acid, 50 per cent v/t>.— -Add 1 volume of concentrated sulphuric acid
(2) to 1 volume of distilled water.

* rt r ?rafSfe °,J Per cenf solution.— Dissolve 0.1 g. of methyl orange in 25 ml

of 0.1/N sodium hydroxide and make upto 100 ml. Filter if necessary,

rr -4* ^-J°neS' 5' £" ?^nEaylSr' G" The termination of Alcohol in Blood and
Unne. The Analyst, March 1954 ; B. M. A. report on The Recognition of Intoxication,

1954;.