H test paper is mainly used to test the acidity and alkalinity of the solution, which can be bought in pharmacies, chemical factories or some stationery stores. Drop the solution onto the test paper, the color of the test paper appears to change, according to the color of the test paper to compare the color card, you can easily and quickly understand the acidity and alkalinity of the solution. When you buy test strips there is usually a standard colorimetric card used for comparison, if it is an error in understanding and you want to buy the early pregnancy test strips, you usually buy them in pharmacies. There are several types to choose from, and those from regular manufacturers are generally more accurate. The urine is usually tested when it is 7-10 days past the menstrual period and the morning urine is more accurate, these test strips are cheaper and easier to buy.