Testing stability

The Arrhenius rate equation forms the basis for the theory behind this accelerated testing. This states that for every 10 °C increase in temperature, the rate of reaction doubles. Thus, in theory, the following applies  

In practice, perfumery companies test all products at 0-4 °C, 20 or 25 °C and 37 °C (or 40 °C) for 12 weeks as a minimum standard. In addition, tests at 45 or 50 °C may be used (except for aerosols, which could explode) if quick results are required, or if it is likely that the product will experience these sort of conditions during its life-cycle. Stability for 4 weeks at 50 °C is considered acceptable in many instances, but signs of instability should be taken as precautionary only, particularly if the samples still appear satisfactory at 37 or 40 °C. This is because certain chemical reactions could occur at these high temperatures that could not happen at ambient temperatures or even at 37 °C. Note that 37 °C has become an accepted standard because many cosmetic chemists believe there is a temperature barrier , corresponding to the heat of the human body, above which chemical reactions are accelerated beyond that predicted by the Arrhenius equation. 

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Use a forced convergence method. Give the calculation an extra thousand iterations or more along with this. The wave function obtained by these methods should be tested to make sure it is a minimum and not just a stationary point. This is called a stability test. 

Thermal stability test by D3241 to meet 3.3 kPa (25 mm Hg) pressure drop and Code 3 Deposit Rating. 

Enamels have very varied properties where their chemical stability is concerned. Relevant stability testing must be carried out for the different areas of application. Enamel coatings for hot water heaters, their requirements and combination with cathodic protection are described in Section 20.4.1. 

In the same way that the Routh-Hurwitz criterion offers a simple method of determining the stability of continuous systems, the Jury (1958) stability test is employed in a similar manner to assess the stability of discrete systems. 

The array for the Jury stability test is given in Table 7.4 where... 

The seript file examp75.m simulates the Jury stability test undertaken in Example 7.5. With the eontroller gain K in Example 7.5 (Figure 7.14) set to 9.58 for marginal stability see equation (7.75), the roots of the denominator of the elosed-loop pulse transfer funetion are ealeulated, and found to lie on the unit eirele in the z-plane. 

StabiLitMts-prufer, m, stability tester, -pnifung, /, stability test. 

HHS/FDA International Conference on Harmonisation Stability Testing of New Drug Substances and Products Guideline Availability Notice, Federal Register, September 22, 1994... 

Electrical Stability of Emuisions. The electrical stability test indicates the stability of emulsions of water in oil. The emulsion tester consists of a reliable circuit using a source of variable AC current (or DC current in portable units) connected to strip electrodes. The voltage imposed across the electrodes can be increased until a predetermined amount of current flows through the mud emulsion-breakdown point. Relative stability is indicated as the voltage at the breakdown point. 

Fig. 3.2.7 Left panel Effects of temperature on the luminescence intensity and stability of the protein P from Meganyctiphanes. The initial light intensity was measured with F plus P in 5 ml of 20 mM Tris-HCl/0.15 M NaCl, pH 7.5, at various temperatures. In the stability test, P was kept at the indicated temperature for 10 min, then mixed with 5 ml of 25 mM Tris-HCl/1 M NaCl, pH 7.59, containing F, to measure initial light intensity. Right panel Effect of the concentration of salts on the light intensity of the luminescence of F plus P, in 25 mM Tris-HCl, pH 7.6, at near 0°C. In the case of NaCl, the light intensity decreased to about a half after 10 min. From Shi-momura and Johnson, 1967, with permission from the American Chemical Society.

Manometric Stability Tests. Based on press measurements developed by gases formed on decompn of ex pis. Am on this group of tests are (1) Brame s Method, (2) Chiaraviglio and Corbino Method, (3) Desmaroux Method, (4) Dupre s-Vacuum Test, (5) Farmer s Vacuum Stability Test, (6) Haid, Becker Dittmar Test, (7) Meerscheidt-Hullassem s Test, (8) Mittasch s Method, (9) Obermuller s Method, and (10) Talliani Test... 

Marqueyrol s Stability Test. 200g samples of double-base powds were heated at 50° under vac in a round bottom Pyrex flask. Every 3—4 days, the vapors were pumped out, collected in, a gasometer over Hg and measured. The test was contd until the powd started to decomp very rapidiy, usually after 1800—2000 days. A curve was then plotted of cc of gas evolved vs days of heating, and the gas was analyzed for C02 and NO. If any liq formed, it was collected, measured and analyzed... 

Mayrhofer Stability Test. A modification of the Bergmann-Junk Test (see Vol 2, B102-R) for testing the stability of NC and propellants. Mayrhofer recommended the use of 20ml of a 2% Kl soln instead of w for the quant collection of decompn products. He also tested NG contg propints in both dry and si moist states, and found that while a stable sample behaved in a similar manner whether heated dry or moist, an unstable powd decompd rapidly in the presence of traces of w. Tonegutti (Ref 3) considered this test reliable for ballistites and unreliable for cordites... 

Vacuum stability. Gas evolution was 1.92 mg/g/40 hours (material recrystd twice from et chloride iso-Pr ale 9 1) 0.89-0.98ml/g/40 hours (sample dried at 40c in vacuum) (Ref 11, p 30). Another stability test, developed by W.C. 

Mercury (Quicksilver, Hydrargyrum), Hg, at wt 200.61, silvery liq, mp —38.87°, bp 356.9°, d 13.546g/cc at 20°. Insol in w, HC1, ale and eth sol In nitric acid. Sometimes found native poisonous. Can be prepd by heating the ore cinnabar (HgS) either in air or with lime. Forms numerous salts, some of which are very expl, eg, Hg fulminate, Hg azide, etc. The presence of Hg in expls, even in minute quants, is unde-sireable because it affects the result of thermal stability tests. Marshall (Ref 1) describes various tests used in Engl and Ger for its detection in different expls and propints Refs 1) Marshall 2, 708-12(1917) 2) Mellor... 

A report was made of any evidence of deterioration, and special stability tests were run on the lot in question (Ref 3)]... 

Stability. In 100° Heat Test loses 2.5% wt in first 48 hours and 1.8% in second 48 hours no expl in 100 hours. In 100° Vacuum Stability Test, evolves 1.9cc of gas per g in 40 hours not considered very satisfactory Volatility. At 60°, loses 24mgs/cm2 in 1 hour... 

Pipes, Table of Military High Explosives , Second Revision, NAVORD 87-46 (July 1946) 16) W.R. Tomlinson, Jr L.H. Eriksen, Stability Tests of Aluminized Explosives , PATR 1635 (21 Oct 1946) 17) A.N. Campbell ... 

Mittasch Stability Test for Nitrocellulose. A test based on the measurement of press developed on decompn of NC. The app may be considered a very complicated modification of devices originated by Abel (Ref 4, p 241) and Hess (Refs 1 4). Abel heated NC samples in vac and detd the press increase. Hess believed that on heating NC in a closed vessel contg air, connected to a Hg manometer, it would be possible to achieve conditions more closely resembling those in storage in closed magazines. Neither of these methods found any practical application... 

Heat Tests. International heat test at 75° resulted in a 0.05% wt loss. It is not appreciably affected by storage after one year at 50° (Refs 14, 19 20). Vacuum stability test at 120° -... 

It is an expl which is as powerful as TNT (99% by ballistic mortar), but more sensitive to impact, being comparable to Tetryl. Its 120° Vacuum Stability Test yields 8cc for a 5g sample in 8 hours, as compared with 6.5cc/5g sample in 15 hours for PETN and 3.8cc/5g sample in 48 hours for Tetryl Refs 1) Beil, not listed in General Index 2) L.F. Fieser W.H. Daudt, JACS 68, 2248-9 (1946)... 

Expln temp is above 360°. Impact sensy is 50cm using a BM machine. Hygry test at 90% RH showed gain of 0.88%, and at 100% RH a gain of 1.61% was demonstrated. The International Heat Test at 75° showed a 1.1% loss of wt. Stability testing at 135° for 300 mins showed no acidity or expln. Vacuum stability a 5g sample yielded 12cc of gas in 48 hrs (Ref 3)... 

Heat Test. Loss 1st 48 hrs 0,07% loss 2nd 48 hrs 0.00% explosion in 100 hrs none Hygroscopicity. % wt gain at 30°, 90% RH trace Vacuum Stability Test, cc/40 hrs at 90° none 100° none 120° 0.11 Sand Bomb Test (200g). 16.3 g sand Sensitivity to Initiation. Minimum detonating charge, g LA 0.20 Tetryl 0.25 Solubility. g/lOOcc solvent in water at 100° 0.10 NB at 150°, <15. Sol in acet ac, nitric acid, caustic potash v sol in dimethyl form-amide insol in ethyl ale, benz, butyl acetate, CC14 ethyl ether (Ref 6)... 

Nomenclature Autoignition Temp, °C Gap Test, 50%, Inches Impact Sensitivity Rifle ttuiiet Impact Test Vacuum Stability Test (ml/g/48hrs 120°) Refs... 

CA 31,5165 (1937) 4)P.Hayard, Vacuum Stability Tests on Solventless Double Base Powders Containing Various Stabilizers OSRD 5959 (20 Nov 1945), 28 Fig 32 5) J.G. Grasselli ed, Atlas of Spectral Data and Physical Constants for Organic Compounds ,... 

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