Chemical test

“ The qualitative test usually used consists in passing the gas-air mixture through a heated quartz tube, which liberates free chlorine. The chlorine may be detected by passing through a potassium iodide solution containing starch, or by the use of a heated copper wire gauze, when the characteristic green color is obtained.
An interesting physiological test has also been developed. The eye has been found to be very sensitive to chloropicrin. The gas affects the eye in such a way that its closing is practically involuntary. ”

“ Since physiological tests are, in many cases, much more sensitive than chemical tests, they have often been used for the identification of traces of poison isolated from a body. Thus a small quantity of a particular alkaloid will produce certain characteristic physiological results when injected into the circulatory system of a small animal, and should precisely the same results be obtained by the injection of the unknown substance, the obvious inference to be drawn is that the two substances are identical. ”

“ If the mixture is deeply coloured, none will act characteristically. If carbonate of potass be present in such proportion as is often met with in the shops, the tests cannot be trusted to.
Process for Compound Mixtures.—The following method of analysis is applicable to all mixtures, organic and inorganic. Add water, if necessary, and filter; and if the fluid which passes through is tolerably free from colour, test a little of it with solution of starch and chlorine. ”

“ I tend to think of human beings as huge, rubbery test tubes, too, with chemical reactions seething inside. When I was a boy, I saw a lot of people with goiters. So did Dwayne Hoover, the Pontiac dealer who is the hero of this book. Those unhappy Earthlings had such swollen thyroid glands that they seemed to have zucchini squash growing from their throats.
All they had to do in order to have ordinary lives, it turned out, was to consume less than one-millionth of an ounce of iodine every day.
My own mother wrecked her brains with chemicals, which were supposed to make her sleep.
When I get depressed, I take a little pill, and I cheer up again. ”

“ If a large number of observations are to be made, an acid may be prepared so that each c.c. equals 1 mgrm. of quinine. A reagent of general application is found in the so-called Mayer’s reagent, which consists of 13·546 grms. of mercuric chloride, and 49·8 grms. of iodide of potassium in a litre of water. Each c.c. of such solution precipitates—
The final reaction is found by filtering, from time to time, a drop on to a glass plate, resting on a blackened surface, and adding the test until no precipitate appears. ”

“ Animal tissues and liquids containing organic matter are best prepared for testing for arsenic by Marsh’s test, in the following manner proposed by Odling:—The tissue, or the residue obtained by the evaporation of a liquid over a water-bath, is to be thoroughly dried at a temperature of about 212° F., then ground to powder or cut up into small pieces, next drenched with the strongest hydrochloric acid and allowed to stand twenty-four hours in a warm place, and finally distilled. ”

“ A chemist, given a liquid to examine, would naturally test first its reaction, and, if strongly alkaline or strongly acid, would at once direct his attention to the mineral acids or to the alkalies. In other cases, he would proceed to separate volatile matters from those that were fixed, lest substances such as prussic acid, chloroform, alcohol, and phosphorus be dissipated or destroyed by his subsequent operations. ”

“ Again, we have the Euchlorine test, in which the procedure is as follows:—A test-tube is taken, and concentrated hydrochloric acid is allowed to act therein upon potassic chlorate. After the gas has been evolved for from 30 to 40 seconds, the liquid is diluted with 11⁄2 volume of water, the gas removed by blowing through a tube, and solution of strong ammonia poured in so as to form a layer on the top; after blowing out the white fumes of ammonium chloride, a few drops of the sample to be tested are added. ”

“ From these the proportions of their elements are easily calculated. The estimation of the quantity of nitrogen (as is also the case with chlorine, phosphorus, sulphur, &c.) requires a separate operation. The two great classes of organic bodies (azotised and non-azotised) are readily distinguished from each other by heating a small portion with some solid hydrate of potassium, in a test tube. If nitrogen is present, it is converted into ammonia, which may be recognised by its characteristic odour and its alkaline reaction.
1. Estimation of the CARBON, HYDROGEN, and OXYGEN.—a. ”

“ There is no test-paper which can be made practically useful as a quantitative test for carbonic acid. (Sanitary Engineer.)
Water.—The tests for water embrace impurities which affect the character of water for drinking, cooking, and washing purposes. Drinking-water should not be too soft, as it provides much of the lime required in building up the bones of the body; the chief evil in drinking-water is the presence of organic ferments. For cooking and washing purposes, water cannot be too soft, and, if used boiled, the presence of organic matters is practically neutralised. ”

“ It hence follows, that mere qualitative tests for these elements in the tissues or fluids of the body are of not the slightest use, for they are always present during the life of the healthiest individual, and can be found after death in persons dying from any malady whatever. To establish the fact of a person having taken an unusual dose of any of the alkali salts, by simply chemical evidence, it must be proved that the alkalies are present in unusual quantities or in an abnormal state of combination. ”

“ Alcohol, Glycerine, and Water Mixture is used as a temporary mounting medium and as a qualitative test for fixed oils.
Chlorzinc Iodide is used as a test for suberin, lignin, cellulose, and starch.
Analine Chloride is used as a test for lignified cell walls of bast fibres and of stone cells.
Phloroglucin. A one per cent alcoholic solution is used in connection with hydrochloric acid as a test for lignin.
Hæmatoxylin-Delifields is used as a test for cellulose.
Fig. 38.—Reagent Set REAGENT SET
Each worker should be provided with a set of reagent bottles (Fig. 38) . ”

“ The carbonate of lime test is to be made first. Four test tubes will be used. In the first we put distilled water alone; in the second we put ten drops of the chalk solution; in the third we put twenty drops of the solution; in the fourth we put thirty drops, then add distilled water till all the test tubes are about two-thirds filled. Drop into each tube about the same quantity of oxalate of ammonia solution, and the degree of turbidity will help to indicate the hardness of each specimen. The first tube, containing pure water, will give no re-action if the chemicals are pure. ”

“ A few glass rods in short lengths do for stirrers. A little ingenuity is better than much apparatus.
Of reagents, all those to be found in a well-appointed laboratory may occasionally be of service, but the rough and ready prospector can get along fairly well with the following: Carbonate of soda, borax, microcosmic salt, cobalt solution, cyanide of potassium, lead granulated, bone ash, test papers of blue litmus and turmeric, the former for proving the presence of acid in a solution and the latter that of an alkali. ”

“ Too much care cannot be taken to ensure the test-liquid, whether for alkalies or acids, being of the proper strength, of which the specific gravity alone is an insufficient proof. In practice, so small a quantity only of test-acid as that referred to above is, of course, seldom made; but as any larger quantities are mere multiples of the smaller one, the necessary proportions to be employed are easily calculated. The common plan is to prepare one or more gallons or quantities of 10 lbs. ”

“ The methods of chemical analysis may be classified according to the type of reaction: (1) dry or blowpipe analysis, which consists in an examination of the substance in the dry condition; this includes such tests as ignition in a tube, ignition on charcoal in the blowpipe flame, fusion with borax, microcosmic salt or fluxes, and flame colorations (in quantitative work the dry methods are sometimes termed “dry assaying”) ; (2) wet analysis, in which a solution of the substance is treated with reagents which produce specific reactions when certain elements or groups of elements are present. ”

“ Biological monitoring has the potential to assess worker exposure to industrial chemicals by all routes, including inhalation, skin absorption, and ingestion. Selection of an appropriate biomarker for an exposure requires knowledge of the distribution, metabolism, and excretion of the toxicant sufficient for selection of the proper compound to be determined, biological medium to be sampled, and time for obtaining a specimen. Often, most of the toxicological and pharmacological information available is from experimental animals and, thus, not always directly applicable to humans. ”

“ Calibrate the spectrometer according to manufacturer's recommendations. NOTE: Typically, an acid blank and 10 μg/mL multielement solutions are used. Analyze a standard for every ten samples. Check measurement recoveries for all elements of interest with at least three spiked, unexposed samples or with reference materials of known elemental composition. These quality control samples should constitute 15 to 20% of all samples analyzed. NOTE: For blood or tissue spikes, split a control sample and spike one fraction. ”

“ After the initial development experiments for the method have been completed and a method has been proposed, the sampling and analysis approach should be evaluated to ensure that the data collected provides reliable, precise, and accurate results. Specifically, the goal of this evaluation is to determine whether, on the average, over a concentration range of 0.1 to 2 times the exposure limit, the method can provide a result that is within ±25% of the true concentration 95% of the time. For simplification, the true concentration is assumed to be represented by an independent method. ”

“ Check for chemical agents before collecting a biological sample/specimen. Chemical agents can damage or destroy biological agents. Also, chemical agents not identified in the sample/specimen can pose a hazard to receiving laboratory personnel. Mark all samples that are potentially contaminated with chemical agents as such.
3. Precautions should be taken to protect the sample/specimen collector from potential BW agents; at a minimum, respiratory protection and rubber gloves must be worn. Additional care must be taken when collecting samples/specimens to prevent cross-contamination. ”

“ When working with concentrated acids, wear protective clothing, safety goggles and gloves. All work should be performed with adequate ventilation for personnel and equipment. It is imperative that acid be added to water in order to avoid a violent exothermic reaction. SAMPLING: 1.
Calibrate each personal sampling pump with a representative sampler in line. NOTE: See NMAM guidance chapters for discussion on sampling. 2. Sample at an accurately known flow rate between 1 and 4 L/min (± 5%) for a total sample size of <1 to 2000 L (see Table 1) for TWA measurements. ”

“ The most delicate test for alcohol is, however, the iodoform test fully described in “Foods,” p. 375. [161] Dichloride of ethylene is detected by shaking up the chloroform with dry potassic carbonate, and then adding metallic potassium. This does not act on pure chloroform, but only in presence of ethylene dichloride, when the gaseous chlor-ethylene (C2H3Cl) is evolved. Ethyl-chloride is detected by distilling the chloroform and collecting the first portions of the distillate; it will have a distinct odour of ethyl-chloride should it be present. ”

“ Of special methods for the separation and detection of mercury, Ludwig’s [945] is, without a doubt, the best when organic matters have to be dealt with; the finely divided solid substances are boiled for some hours with hydrochloric acid, strength 20 per cent.; then the liquid is cooled to 60°, and potassic chlorate added in half gramme quantities until the dark liquid becomes clear; the liquid is cooled and filtered, and the substances on the filter washed with water. ”

“ Consequently, a measured quantity of acid should be used in each assay and a comparative experiment made with a known weight of pure carbonate of lime which will yield about the same volume of gas. The number of c.c. of gas got in the assay multiplied by 4.7 will give the number of milligrams of pure carbonate of lime that must be taken for the standard. With ordinary work the error rarely exceeds half a c.c. ”

“ Allow the preweighed area filter samples to equilibrate 24 h with the laboratory atmosphere. b. Weigh the area filters. Determine total weight collected on each. c. Extract the first pair of area filters with acetronitrile, the second with benzene, the third with cyclohexane, and the fourth with methylene chloride, according to step 8. NOTE: Use alternate solvents, if appropriate. PAH of interest may be entrained within, and adsorbed by, particulate matter collected on the filter. It is necessary to determine the solvent which maximizes recovery of the PAH from each sample matrix. ”