Volumes and Dilutions

The volume of water used to inoculate media depends on the expected levels of microbial contamination. In the case of counts on pour plates, 1 ml of water is placed in the plate and 9 ml of molten nutrient agar is added. The water may be used neat if it is of good quality, but should be diluted aseptically if of poor quality (see below). The agar should not be too hot (kills bacteria) or too cool as it will form lumps on pouring. The recommended temperature is 50-55 °C. 

The volumes normally used for water of reasonable quality in tube counts are 50 ml of water inoculated into one 50 ml tube of double strength medium, 10 ml into each of five tubes containing 10 ml of double strength medium, and 1 ml into each of five tubes containing 10 ml of single strength medium. If the quality of the water is doubtful, then the 50 ml sample should be omitted, and be replaced with 

1ml samples inoculated into each of five tubes containing 10 ml of single strength medium. A fresh sterile pipette should be used for each inoculation. 

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The acetic acid mother liquor, containing the rest of the reaction product, was concentrated in vacuo. The residue was dissolved in methylene chloride and washed with ice cold sodium carbonate solution. The organic solution was dried, concentrated in vacuo to a small volume and diluted with ether and petroleum ether. Fine yellow needles of 2-chloro-methyl-4-phenyl-6-chloroquinazoline 3-oxide precipitated. The pure base was recrystallized from a mixture of methylene chloride, ether and petroleum ether, MP 133° to 134°C. 

To a stirred suspension of 10 grams (35 mmol) of 7-chloro-5-phenyl-3H-1,4-benzodiazepin-2(1H) one 4-oxide in approximately 150 ml of methanol was added in portions an excess of a solution of diazomethane in ether. After about one hour, almost complete solution had occurred and the reaction mixture was filtered. The filtrate was concentrated in vacuo to a small volume and diluted with ether and petroleum ether. The reaction product, 7-chloro-1-methyl-5-phenyl-3H-1,4-benzodiazepin-2(1 H)-one 4-oxide, crystallized in colorless prisms. The product was filtered off and recrystallized from acetone, MP 188°-189°C. 

Analysers for clinical purposes have been designed [129-131] and even a bedside analyser for monitoring Na, K, Cs and jJ-D-glucose in patients blood [127] or a blood potassium analyser for use during open-heart surgery [109]. A computer-controlled interference correction has been proposed [44], in which the standards are mixed to match the electrode potential obtained in the test solution. A simple caUbration in flow systems [61] involves dilution of the standard solution and monitoring of the ISE potential as a function of the diluent volume and dilution time. 

D-eryf/iro-V7-Benzyl-(5-niethyl-N-(9-phenylfluoren-9-yl)aspartic Acid a-Methyl Ester (74) 271 To P-methyl-substituted ester 73 (4.19 g, 8.28 mmol) in THF (150 mL) was added MeOH (45 mL) and the soln was heated to 60 °C. LiOH-H20 (3.47 g, 82.8 mmol) in H20 (90 mL) was added over 10 min and the mixture was stirred at 60 °C for 24 h. After cooling to rt, it was washed with Et20 (2 x) and the organic phases were back-extracted with H20 (2 x). The aqueous phases were acidified with sat. citric acid and extracted with EtOAc (2 x). The combined EtOAc extracts were washed with H20 (1 x) and brine (1 x), concentrated to one-half volume, and diluted with hexanes. The desired epimer (l.64g) was obtained as a solid, and the mother liquors were chromatographed on silica gel (EtOAc/hexanes 1 3) to give additional 74 (1.12 g) total yield 69%. 

In practice, dilutions are carried out as shown in Figure 3.4. The volume to be diluted is withdrawn using a calibrated tube called a pipet, placed in an empty volumetric flask of the chosen volume, and diluted to the calibration mark on the flask. 

Hydroxy-6-methoxybenzaldehyde (16.875 g, 0.111 M), ethyl 5-bromopentanoate (23.25 g, 17.6 ml, 0.111 M), anhydrous potassium carbonate (16.5 g), sodium iodide (0.675 g) and 95% ethanol (150 ml) were refluxed with stirring (16 hours). The cooled reaction mixture was filtered and the solid washed well with ethanol. The filtrate was evaporated to dryness and the residue partitioned between ether and water. The ethereal layer was separated and washed with 2 N sodium hydroxide solution, water, dried (sodium sulfate) and evaporated. The residue was dissolved in 95% ethanol (300 ml) and 0.66 N sodium hydroxide solution (450 ml) and stirred at ambient temperature (4 hours). The reaction mixture was evaporated to half volume and diluted with water. The mixture was extracted once with ether and the aqueous layer acidified with concentrated hydrochloric acid with cooling. The crystalline solid formed was filtered off and washed well with water. Recrystallisation from ethyl acetate-petrol gave 5-(2-formyl-3-methoxyphenoxy)pentanoic acid, melting point 99-101°C. 

Yates, W.E. Akesson, N.B. Coutts, H.H. Drift hazards related to ultra-low-volume and diluted sprays applied by agricultural aircraft. Trans. Am. Soc. Agric. Engrs., 1967, 10, 628. 

Fruits and fruit products. Weigh 300 g of jelly, syrup, fresh or dried fruit or preserve into a 21 beaker, add ca. 800 ml of water and extract by gently boiling for 1 h, replacing water lost by evaporation. Filter into a 21 volumetric flask, cool, dilute to volume, and dilute again if necessary to bring the analyte concentration to a level suitable for FAAS. 

Alternatively, digest an accurately weighed amount of sample according to any of the two wet-digestion procedures described in Sections III.A.l— III.A.2, transfer to a volumetric flask of suitable volume and dilute to volume. Use this solution directly for FA AS. 

To a warm solution (50 °C) of the 2-aminodiphenyl ketone oxime (70 g, 0.33 mol) in glacial HOAc (420 mL) was added chloroacetyl chloride (74.6 g, 0.66 mol). The mixture was left at rt for 48 h, saturated with anhyd HCl (g), and concentrated in vacuo. The residue was dissolved in CHjClj and washed with ice-cold NajCO soln. The organic solution was dried, concentrated to a small volume, and diluted with petroleum ether. The precipitated crystals were filtered. The mother liquid yielded an additional crop. After recrystallization, the product formed as yellow needles yield 67.8 g (76%) mp 160-161 °C. 

Standard gold solution 1 mg/ml. Dissolve 0.1000 g of suitably pure gold in 4 ml of aqua regia, and evaporate the solution nearly to dryness. Add 2 ml of cone. HCl, evaporate to half the volume, and dilute the solution with water to the mark in a 100-ml standard flask. The stability of gold solutions has been discussed [42,43]. 

The separation of Th as the sparingly soluble thorium fluoride is equally selective [4]. The solubility of ThF4 is lower than that of the oxalate. Usually, the sample solution in hydrofluoric acid is evaporated to a small volume and diluted with water to precipitate Th, U(IV), and rare-earth metals. La, Ce, or Ca are used as collectors for traces of Th. Since the fluoride precipitate is difficult to filter off, centrifugation is advisable. 

Glycinin and p-conglycinin have several subunits that can be dissociated by salt solution. Murray et al. (1980) patented a process that employs salt for extracting SPI at ionic strengths of 0.3 to 0.6 M, pH 5.0 to 6.8 and 15 to 25°C (60 to 78°F). The extract is then concentrated to one-fourth to one-third its volume and diluted to an ionic strength of <0.2 M to form protein micelles that precipitate into an amorphous mass and are dried or further processed. 

Birks, 1964). This technique is limited to small volume and dilute aqueous samples. 

Note 10— The formation of NO and NO from oxidative combustion of nitrogen containing hydrocarbons is dependent on combustion conditions such as temperature and oxygen concentration. Injection of a constant solution volume, and dilution of all test specimens and standards with a common solvent, maintain consistent combustion conditions for test specimens and standards. 

Adding water (solvent) to the soup increases the volume and dilutes the tomato soup concentration. 

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