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0.25
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huyuchem(金币+1):鼓励
H2SO4 + NaCl => HCl(g) + NaHSO4
(The reaction of sodium bi-sulfate and table salt to produce hydrogen chloride only takes place at elevated temperature (+250篊).) Hive Bees fervently defend this method of dripping sulfuric acid over table salt, yet it is inferior to the recommended method for these reasons:
The salt/sodium bi-sulfate cake in the bottom of the reactor cannot be stirred using a magnetic stirrer, and it can be seen that even with overhead stirring (using a seal) the cake cannot be easily stirred, and without stirring the reaction is slow and yield is much less than theoretical.
The production of HCl(g) cannot be controlled by controlling addition of sulfuric acid, since sulfuric acid builds up around the salt cake and reacts independently of the dripping.
The salt/sodium bi-sulfate cake cannot be removed from the reactor without taking the apparatus apart, which fills the area with HCl vapor as a result. Therefore, rapid unload and reload is not possible, limiting the amount of hydrogen chloride that can be produced in a day.
The salt/sodium bi-sulfate cake does not easily come out of the reactor, but requires washing with hot water and shaking to dislodge. Producing 3 to 10 kilograms of HCl(g) using this method and a 5L reactor would take substantial effort and time and would release an undesirable amount of HCL vapor into the work area, compared to the recommended method. Overall this method is inferior.
A third method is heating table salt and sodium bisulphate. The reaction mechanism is:
NaCl(s) + NaHSO4(s) + delta temp. => HCl(g) + Na2SO4(s)
This method is also inferior for the following reasons:
The temperature in the reactor must reach +250篊 for the reaction to commence. Microwaves has been used.
Although stirring is not required, because the two powders are mixed before charging the reactor, the yield is much less than theoretical because the two compounds can never come into intimate contact.
A very hard cake of salt/sodium sulphate remains in the reactor after cooling. This cake can only be removed with copious amounts of hot water and much shaking and cursing. Time is wasted while heating the mix, time is wasted while waiting for it to cool down, time is wasted removing the cake from the reactor. Impossible for larger scale production.
A fourth method is boiling muriatic acid. The idea is to reduce the solubility product of HCl in water by boiling muriatic acid. However, hydrogen chloride forms a constant boiling mixture with water, such that a great deal of water vapor comes over with the HCl and quickly dilutes the sulfuric acid bubbler. Yield is unacceptable compared to any of the above reactions. Although the reactor can be pumped or siphoned out and reloaded, the remaining liquid still contains substantial amounts of HCl which even cooled and poured into water releases HCl vapor into the work area, very unpleasant to handle, and not something to pour down the drain since it is highly corrosive. An inferior method and not recommended at all. |
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