The surfactant used in this synthesis is tetramethylammonium hydroxide (N(CH3)4OH ). The hydroxide (OH) ions formed in solution tend to bind to the iron sites on the magnetite particles, creating a net negative charge on each particle. The positively-charged tetramethylammonium ions will then associate with the negatively-charged magnetite particles, forming a kind of shell around each magnetite particle. This charged shell raises the energy required for the particles to agglomerate, stabilizing the suspension.
* This experiment is based on syntheses described in the following papers: (1) Palacin, S.; Hidber, P.C.; Bourgoin, J.; Miramond, C.; Fermon, C.; Whitesides, G. 1996, 8, 1316. (2) Jolivet, J.P.; Massart, R.; Fruchart, J. M. Nouv. 1983, 7, 325. (3) Enzel, P.; Adelman, N.B.; Beckman, K.J.; Campbell, D.J.; Ellis, A.B; Lisensky, G.C., 1999, 76, 943. We also thank Jonathan Breitzer for his modifications of the original procedure.
(1983) Survival and growth of warmwater fishes exposed to ammonia under low flow conditions, Springfield, Virginia, National Technical Information Service (NTIS PB83-257535).
Hydrolysis of ethanoic anhydride
This is possibly because of the conversion of most of the available ammonia to N-chloramines (mono-, di-, and tri-chloramines) during the chlorination of drinking-water (Morris, 1978), which reduces ammonia concentrations to levels below analytical detectability.
Gaseous and anhydrous liquid ammonia
If a person breathes an ammonia concentration in air of 18 mg/m3 (a common occupational exposure limit) at 1 m3/h and, if all the ammonia is retained, then 18/60 = 0.3 mg ammonia/min would require to be cleared by hepatic blood flow (say 1 litre/min).
Sources releasing ammonia into the air
Because ammonia is very water soluble, and thus absorbed by the mucous coating in the upper respiratory tract, the lungs are protected from the effects of exposure to low concentrations of ammonia (Haggard, 1924; Boyd et al., 1944).
Sources discharging ammonia into water
It should be noted that experimental animals kept in cages may be exposed to relatively high concentrations of ammonia, even exceeding 100 mg/m3, due to the degradation of urea in urine and faeces (Flynn, 1968; Schaerdel et al., 1983).
Ammonia will adsorb on various solids.
An arterial fasting ammonia concentration of 1.05 mg/litre has been reported in healthy subjects (Conn, 1972), so the calculated rise is only 10% over fasting levels.
Heating solutions or crystals of the salts yields gaseous ammonia.
At ammonia concentrations of between 40 and 350 mg/m3 (57 and 500 ppm) and a mean minute volume of 6 - 7 litre/min, for short durations (< 2 min), they found that approximately 92% ± 2% was retained in the respiratory system (i.e., mouth, lungs, etc.) in 2 male volunteers, tested 4 times.
Ammonia forms chloramines in water containing hypochlorous acid.
In another study (Kustov, 1967), exposure of human volunteers to ammonia for a longer duration (14 mg/m3 (20 ppm) for 8 h) was accompanied by a statistically-significant increase in BUN from 23.9 to 30 mg%.