Dilution-ratio tests

The first element, dynamic dilution, provides a reproducible sample for each panelist. The system must minimize the loss of the odorant to the walls of the delivery apparatus, provide clean dilution air of odor-free quality, maintain a constant dilution ratio for the duration of a given test, and have no memory effect when going from high to low concentrations or switching between odorants of different character. The type of mask or port and the delivery flow rate have been found to influence the response of panelists in determining odor threshold and intensity. 

In the presence of bromide ions the electrode was subject to a drop in potential, (e.g., 1.5 to 5.7 mV at a Br iCl ratio of 2000 3) and to delayed response. A considerable hysteresis effect is also observed in concentrated solutions of chloride when the electrode is used in a 1M chloride solution and then dipped in one that is 0.02 M. Equilibrium is reached only after 10 min. The junction potential is minimised by diluting the test solution with the salt-bridge solution (10% aq. potassium nitrate). 

Table 3. EDAR index application for the hazard assessment of water samples and pure compounds using a battery offive toxicity tests. Effect dilution ratio values are indicated for each test.

Resistivity measurements were conducted on a number of representative insecticides selected from several major formulation categories as listed in Table I. Readings were taken at room temperature (=20 0) and 1000 Hz using a dip-type conductivity cell (0.10 cm constant) operated in conjunction with an autobalance digital Impedance meter. All test liquids were measured at 16 dilution ratios (-c.e., distilled water commercial formulation) ranging from 0 1 to 80 1 on a volume basis. 

Figure 5 depicts the typical resistivity response measured as a function of dilution ratio. Maximum values for each material tested were obtained for the undiluted formulation, with minimum values occurring immediately upon small dilutions at ratios of typically 1 2 to 4 1. Additional dilution resulted in a gradual Increase in the resistivity of the test liquids. It appears that Initial dilution with the distilled water caused molecular... 

Serial dilutions of the patient s serum are used to establish a Tg antibody titer. The reported result is the highest dilution that causes agglutination. Titers are usually considered negative at a less than 1 10 dilution ratio. This hemagglutination test is not highly specific, and about 5% to 10%... 

Two standard tests. Kauri butanol (KB) number and dilution ratio, involving simple laboratory equipment can be used and there is a fair correlation (Fig. 13.4) between the former and the Hildebrand solubility... 

Another empirical test to compare the performance of organic solvents is the dilution ratio (Table 13.6). This involves adding dropwise the solvent under test into a toluene solution of cellulose... 

ASTM D 1720-96. Standard test method for dilution ratio of active solvents in cellulose nitrate solutions. ASTM D 5062-96. Standard test method for resin solution dilutabihty by volumetric/gravimetric... 

Tested material Oven temp. Dilution ratio CO-Hb % Mortality ratio (animal)... 

Also the paint industry, formerly the main end-user of solvents, attempted to produce a quantitative solvent power data system [5]. This related solvency to certain standard solutes, used in their industry. These could either be a well-known natural (Kauri-resin) or later a synthetic (nitrocellulose) paint binder. The result was the introduction of the Kauri-Butanol number, which applies to hydrocarbon solvents only and the NC-dilution ratio which is used for oxygenated solvents. Another test, used in conjunction with hydrocarbon solvents, is based on the fact that aniline is hardly miscible with aliphatic hydrocarbons but mixes very well with aromatics. The Kauri-Butanol (KB) number as defined in ASTM D 1133 is a measure of the tolerance of a standard solution of Kauri resin in -butanol to hydrocarbon diluent. Standard hydrocarbon solvents used to calibrate the Kauri solution are toluene (KB-number 105) and a 75% v -heptane/25% v toluene blend (KB-number 40). The KB-value increases from approx. 20 to over 100 in the order ... 

In this study, experimental data on the amount of asphalt and asphaltene precipitation due to addition of solvents to West Sak crude were gathered. The first set of tests were conducted for West Sak stock tank oil. Solvents used include ethane, carbon dioxide, propane, n-butane, n-pentane, n-heptane, Prudhoe Bay natural gas (PBG) and natural gas liquids (NGL). Effect of solvent to oil dilution ratio on the amount of precipitation was studied. Alteration of crude oil composition due to asphalt precipitation was measured using gas-liquid... 

The toluene dilution ratio is used for rating solvency of oxygenated solvents. This test method involves the determination of the volume ratio of toluene to active solvent required to cause precipitation in a standard solution of nitrocellulose. Toluene dilution ratios vary from approximately 6 for very strong solvents to approximately 1.5 for weak solvents. 

One way to check the influence of coincidence is to perform a second measurement at a more dilute concentration. If the particle concentration ratio of the two measurements differs from the known dilution ratio of the two samples, some effects of coincidence in the first measurement are probable and the result should be discarded and a new dilution prepared to test the second sample. Progressive measurements should be made until the reported concentration ratio between two consecutive samples agrees with the toown dilution ratio. The highest concentration at which this occurs is then accepted as the uppermost concentration limit for the instrument used in measuring this material. No specific concentration limit can be specified since this will depend on the particle size distribution, instrument design, and the flow rate. The overall maximum concentration may range from a few particles to a few thousand particles per ml. 

Control of an evaporator requires more than proper instrumentation. Operator logs snould reflect changes in basic characteristics, as by use of pseuao heat-transfer coefficients, which can detect obstructions to heat flow, hence to capacity. These are merely the ratio of any convenient measure of heat flow to the temperature drop across each effect. Dilution by wash and seal water should be monitored since it absorbs evaporative capacity. Detailed tests, routine measurements, and operating problems are covered more fuUy in Testing Procedure for Evaporators (loc. cit.) and by Standiford [Chem. Eng. Prog., 58(11), 80 (1962)]. 

One can test for general acid-base catalysis by varying [BH+] and [B] at constant pH. An easy test is to dilute the buffer progressively at a constant ratio of [BH+]/[B], making up any ionic strength change so as not to introduce a salt effect. If the rate is invariant with this procedure, then general acid-base catalysis is absent under the circumstances chosen. 

Fossil fuel emissions alter the isotopic composition of atmospheric carbon, since they contain no C and are depleted in C. Releasing radiocarbon-free CO2 to the atmosphere dilutes the atmospheric C content, 3delding lower C/C ratios ("the Suess effect"). From 1850 to 1954 the C/C ratio in the atmosphere decreased by 2.0 to 2.5% (Fig. 11-23) (Suess, 1965 Stuiver and Quay, 1981). Then, this downward trend in C was disrupted by a series of atmospheric nuclear tests. Many large fission explosions set off by the United States with high emission of neutrons took place in 1958 in the atmosphere and the Soviet Union held extensive tests during... 

---