Hardness Determination GB69091-86, this standard applies to the determination of the hardness of natural water, cooling water, water samples 'water.
Measuring range; hardness from 0.1 to 5 mmol/L. When the hardness exceeds 5 mmol/L, the sampling volume can be reduced and diluted appropriately to 100 ml before measurement.
In an aqueous solution with a pH of 10.00, use chromium black T as an indicator and titrate with the standard solution of ethylenediaminetetraacetic acid disodium salt (EDTA for short) until that it reaches blue as its final point. The hardness value can be calculated based on the volume of EDTA consumed. In order to improve the sensitivity of end point indication, a certain amount of disodium magnesium salt of EDTA can be added to the buffer solution. If acid chrome blue K is used as an indicator, it can be omitted.
Magnesium saltdisodium EDTA. Iron more than 2 mg, aluminum more than 2 mg, copper more than 0.01 mg, manganese more than 0.1 mg may interfere with the determination. Before adding the indicator, use 2 ml of 1% cysteamine hydrochloride solution and 2 ml of ethanolamine (1+). 4) for masking joints to eliminate interference.
Non-carbonate hardness
Non-carbonate hardness: Hardness mainly formed by salts such as sulfates, chlorides and nitrates of calcium and magnesium. This type of hardness cannot be removed by thermal decomposition, so it is also called permanent hardness, such as CaSO4, MgSO4, CaCl2, MgCl2, Ca(NO3)2, Mg(NO3)2, etc.
The sum of carbonate hardness and non-carbonate hardness is called total hardness; the Ca2+ content in water is called calcium hardness; the Mg2+ content in water is called magnesium hardness when the total hardness of water is called magnesium hardnesstotal rety. is less than the total alkali. The difference between them is called negative hardness.
Air conditioning water hardness requirements: Hardness (calculated as CaCO3): ≤700 mg/L. Air conditioners have requirements for the quality of cooling water replenishment, which must be treated with fresh water. If the added water is not treated, the interior walls of the air conditioner cooling system pipes will become scaled. Over time, small pipes may even become clogged, affecting the heat conduction and cooling effect of the air conditioner. . Many of them do not pay attention to the quality of air conditioning cooling and ice water replenishment, and due to the accumulation of scale, only cleaning the system is laborious and expensive, which also damages the machine .
Specific principle
When the air conditioner cools, the air is exchangedheated through the indoor heat exchanger. At this time, as the air temperature decreases, humidity in the air accumulates. condenses on the surface of the indoor unit heat exchanger and is then discharged outside. People in the room will be very thirsty and uncomfortable. If you put a basin of water in the room from the start, the water may evaporate. so you can Maintaining indoor humidity is beneficial for people, so when using air conditioners, water is always needed.
The air conditioner does not need to add water. This may be because the air conditioner is seriously dehumidifying and the room is easy to dry. You can see that the air conditioner has an old water pipe. This is the reason why the water is leaking. Over time, this will cause sore throat. It is therefore better to spray water in the room or put a humidifiereur. Additionally, make sure the room is ventilated. The air conditioner is not turned on. It is best to change the air well.