Nowadays, more and more people drink mineral water and pure water. Do they produce scale when boiling water? Many netizens may know that pure water will not produce scale, because pure water has no minerals and belongs to pure water.
The question we have to answer immediately becomes simple: when mineral water or tap water is boiled, which produces more scale?
Scale, also known as water alkali, is produced because the hardness of water is too great. Soft water with hardness usually within 0-60 mg/L; More than 60 mg/L is mostly hard water. Therefore, it is generally believed that when the hardness of water exceeds 60 mg/L, scale will appear when water is boiled, and the greater the hardness, the more scale there will be.
The hardness of water is positively correlated with the content of calcium and magnesium ions in water. The more calcium and magnesium ions, the greater the hardness of water. The hardness of water can be calculated by the following formula: hardness = (calcium ion content 2.5+ magnesium ion content 4. 1).
If the content of calcium ion in water is 40mg/L and the content of magnesium ion is 30mg/L, the hardness of water can be calculated as follows: hardness = (402.5+304.1) = 223mg/L. The state stipulates that the hardness of drinking water should not exceed 450mg/L..
Researchers from College of Traditional Chinese Medicine of Henan University, Clinical Medical College of Southwest Medical University and Jilin Normal University tested the hardness of the best-selling bottled drinking water in the market and listed it in the table below. Southwest Medical University did not give the brand name, which may be due to the consideration of brand protection.
The best hardness range of high-quality mineral water is 80-170 mg/L. It can be seen that only Diaoyu Island belongs to high-quality mineral water with more calcium and magnesium minerals, and Evergrande Ice Spring can barely enter this range. The hardness of Nongfu Spring and Baisui Mountain is moderate, that is, the content of minerals such as calcium and magnesium ions is not high, which is why it tastes a little sweet.
Bottled water and distilled water are pure water with almost zero hardness, so there will be no scale when boiling. Only the hardness of Diaoyu Island and Evergrande Ice Spring exceeds 60mg/L, and the hardness of other waters is low, so most bottled water and bottled water will not have scale when boiling water.
The hardness of tap water in most northern cities is above 1.80mg/L, and many of them are even as high as 400 mg/L. For example, the hardness of tap water in Jinzhou City, Liaoning Province is as high as 368.4 mg/L. Because underground well water is used as drinking water source in many northern areas, calcium and magnesium minerals in water are generally high.
In the south, although the hardness of tap water is as high as 150mg/L, for example, it can reach 157mg/L in Wuhan, but the hardness of tap water in most parts of the south is lower, for example, the hardness in most parts of Hangzhou is less than 60mg/L. This is because there are a lot of surface water, lakes, rivers and reservoirs in the south, and there is a lot of rain. Rainwater is soft water without calcium and magnesium ions.
As can be seen from the above analysis, the hardness of water quality can be arranged as follows: tap water in the north >: mineral water > tap water in the south > pure water. In other words, the order of scale should be the same.
Is it too big? Don't!
Scale is actually an indicator to measure the content of calcium and magnesium minerals in water in disguised form, so the scale in tap water in the north shows that there are many minerals in water, while the scale in the south shows that there are not enough calcium and magnesium minerals in water. To some extent, the water in the north contains more calcium and magnesium, which can reflect why northerners are generally taller than southerners.
Therefore, don't blindly use scale to exclude water. Nowadays, many people are drinking bottled water and purified water, which is actually very bad because there are no calcium and magnesium minerals. Look at the hardness of bottled water and distilled water in table 1, both of which are 0, indicating that there is no mineral nutritional value. It's best to drink less, especially when you are short of calcium.
reference data
Cao pengran. Analysis of total hardness of different brands of mineral water in the market. Journal of Henan University.2014,33.
Zhou Peng. Determination of hardness of several commercially available mineral waters. Guangzhou chemical industry. 2016,44.
Du hongxue Analysis of physical and chemical properties of drinking water in Siping city. Liaoning Chemical Industry.2019,48.