外觀判斷

　　Appearance judgment

　　通過外觀上觀察和手感可初步判斷石膏粉質量的優(yōu)劣。就是看石膏粉的外觀顏 色，手感就是用手搓一搓石膏粉的糙細程度(細度）。

　　The quality of gypsum powder can be preliminarily judged by observing its appearance and feel. It depends on the appearance and color of the gypsum powder, and the feel is the roughness (fineness) of the gypsum powder when rubbed by hand.

　　外觀上看，白度高的石膏粉細度數(shù)高，質量好，價格較高；而發(fā)灰發(fā)黑、里面有黑色雜質的石膏粉質量較差。用手的拇指和食指搓捻石膏粉,手感發(fā)沙粗糙的 石膏粉細度糙，質量較差、價格較低；而手感細膩的石膏粉說明細度細，質量較好，價格也會較高。

　　Visually, gypsum powder with high whiteness has a high degree of fineness, good quality, and a relatively high price; The quality of gypsum powder that turns gray and black with black impurities inside is poor. Rub and twist gypsum powder with the thumb and index finger of your hand. Gypsum powder that feels sandy and rough to the touch has a coarse fineness, poor quality, and lower price; The delicate texture of gypsum powder indicates fine fineness, good quality, and higher price.

　　測定結晶水含量

　　Determination of Crystalline Water Content

　　石膏粉是一種結晶混合物，其中會含有生石膏、半水石膏和無水石膏(過燒石膏）。

　　Gypsum powder is a crystalline mixture that contains gypsum, hemihydrate gypsum, and anhydrous gypsum (burnt gypsum).

　　在炒制過程中欠火夾生會出現(xiàn)生石膏,或者火大、炒制時間過長造成過燒會出現(xiàn)無水石膏，這些都會影響石膏的凝結時間,影響生產的正常 使用。有時由于石膏粉放置時間過長受潮,也會影響正常使用。根據(jù)經驗和資料介紹,通過測定結晶水的含量，可判斷石膏粉質量的好壞。一般合格的石膏粉結晶水的含 量在4.5?5.5%之間^若石膏粉的結晶水含量遠低于此標 準值,則說明石膏粉過燒,注模時凝結時間太長甚至不凝 固;若石膏粉的結晶水含量遠高于此標準值，則說明石膏粉欠火或者受潮,注模時凝結時間短。以上兩種情況的石膏粉都不合格,在生產中不能使用。

　　During the frying process, insufficient heat can lead to the formation of raw gypsum, or excessive heat and frying time can result in the formation of anhydrous gypsum, which can affect the setting time of gypsum and the normal use of production. Sometimes, due to prolonged exposure to moisture, gypsum powder can also affect its normal use. Based on experience and information, the quality of gypsum powder can be determined by measuring the content of crystal water. What is the content of crystallization water in generally qualified gypsum powder at 4.5? Between 5.5% ^ If the crystalline water content of gypsum powder is much lower than this standard value, it indicates that the gypsum powder is overheated, and the setting time during injection molding is too long or even not solidified; If the crystalline water content of gypsum powder is much higher than this standard value, it indicates that the gypsum powder is undercooked or damp, and the setting time during injection molding is short. The gypsum powder in both of the above situations is unqualified and cannot be used in production.

　　檢測石膏粉結晶水含量的方法是：準確稱取4(TC 烘干后冷卻至室溫的試樣質量G (—般為2?5g),放 置于恒重的鉑金坩堝（或瓷坩堝）中，準確稱取其質量 為G1;在230±5°C下灼燒2h，取出移人干燥器內，冷 卻至室溫后稱取其質量為G2，則其結晶水百分含量為 (Gt—G2)/GX100%。

　　The method for detecting the crystal water content of gypsum powder is to accurately weigh 4 (the mass G of the sample cooled to room temperature after TC drying is generally 2-5 g), place it in a constant weight platinum crucible (or porcelain crucible), and accurately weigh its mass as G1; Burn at 230 ± 5 ° C for 2 hours, transfer to a dryer, cool to room temperature, and weigh its mass as G2. The percentage of crystal water is (Gt-G2)/GX100%.

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