檢驗(yàn)氫氧化鉀中要確定樣品的采樣單元數(shù)。采樣器由袋口的一角斜到袋深的3/4處采樣，將采出的樣品混勻，用四分法縮分到所要檢驗(yàn)的樣品量。

The number of sampling units of the sample shall be determined in the test of potassium hydroxide. The sampler slants from one corner of the bag mouth to 3/4 of the bag depth for sampling, mixes the collected samples evenly, and reduces them to the amount of samples to be tested by quartering.

因氫氧化鉀肥料吸水性強(qiáng)，故在制備樣品時(shí)動(dòng)作應(yīng)迅速。樣品制備后，稱取5g試樣，到0.001g，加入150ml水，然后在不斷攪拌下加熱，微沸5min，取下冷卻到20℃，移入500ml容量瓶，定容過(guò)濾后再吸取25.0ml于250.0ml的容量瓶中。這是一個(gè)很關(guān)鍵的環(huán)節(jié)。

Because potassium hydroxide fertilizer has strong water absorption, it should be rapid when preparing samples. After sample preparation, weigh 5g of sample to 0.001g, add 150ml of water, and then heat it under constant stirring, slightly boil it for 5min, take it down and cool it to 20 ℃, transfer it into a 500ml volumetric flask, filter at constant volume, and then suck 25.0ml into a 250.0ml volumetric flask. This is a key link.

有一些檢驗(yàn)員為了一時(shí)方便，不是在水溫達(dá)到20℃時(shí)定容，而按常溫的水溫定容，結(jié)果是水溫高于20℃時(shí)，結(jié)果偏高；水溫低于20℃時(shí)，結(jié)果偏低。兩次定容造成兩次誤差，所以，準(zhǔn)確的檢驗(yàn)溫度是檢驗(yàn)結(jié)果準(zhǔn)確與否的關(guān)鍵。水溫高于20℃的檢驗(yàn)結(jié)果與20℃時(shí)的檢驗(yàn)結(jié)果比較見表1。

For temporary convenience, some inspectors do not fix the volume when the water temperature reaches 20 ℃, but according to the normal temperature. The result is that when the water temperature is higher than 20 ℃, the result is higher; When the water temperature is lower than 20 ℃, the result is low. Two times of constant volume cause two times of error, so the accurate test temperature is the key to the accuracy of the test results. See Table 1 for the comparison of the test results when the water temperature is higher than 20 ℃ and the test results when the water temperature is 20 ℃.

在弱堿性介質(zhì)中，四苯硼鈉[NaB(C6H5)4]堿性溶液和洗滌液對(duì)檢驗(yàn)結(jié)果有直接影響。因?yàn)榕渲坪玫乃谋脚疴c很不穩(wěn)定，容易產(chǎn)生渾濁。如果使用前發(fā)現(xiàn)有混濁，要用中速濾紙過(guò)濾后再使用，否則檢驗(yàn)結(jié)果偏高。用洗滌液洗滌和用蒸餾水洗滌檢驗(yàn)，結(jié)果也不一樣。有些檢驗(yàn)員認(rèn)為配制洗滌液麻煩，用蒸餾水代替洗滌液，檢驗(yàn)結(jié)果就會(huì)偏低。蒸餾水的原始結(jié)果與洗滌劑的正確結(jié)果相關(guān)數(shù)據(jù)比較見表1。

In weakly alkaline medium, sodium tetraphenylboron [NaB (C6H5) 4] alkaline solution and washing solution have a direct impact on the test results. Because the prepared sodium tetraphenylboron is unstable and easy to produce turbidity. If turbidity is found before use, it should be filtered with medium speed filter paper before use, otherwise the test result is on the high side. The results of washing with detergent and distilled water are also different. Some inspectors think it is troublesome to prepare washing solution. If distilled water is used instead of washing solution, the test result will be low. See Table 1 for the comparison between the original results of distilled water and the correct results of detergent.

檢驗(yàn)中，試液過(guò)濾后的洗滌步驟存在洗滌終點(diǎn)不夠明確的問題。依據(jù)GB6549-1996《氫氧化鉀》規(guī)定，先抽濾上清液，再用洗滌液（即室溫下飽和的四苯硼鉀溶液）轉(zhuǎn)移沉淀過(guò)濾器中，繼續(xù)用以上洗滌液洗滌沉淀12次左右，每次洗滌液用量約為5ml。

During the test, there was a problem that the washing end point was not clear enough in the washing step after the test solution was filtered. According to the provisions of Potassium Hydroxide (GB6549-1996), the supernatant is filtered first, and then the washing solution (i.e. potassium tetraphenylborate solution saturated at room temperature) is transferred to the filter for precipitation. The above washing solution is used to wash and precipitate for about 12 times, and the amount of washing solution is about 5ml each time.

如果檢驗(yàn)員做不夠洗滌次數(shù)，在干燥后的坩堝上就能清晰見到粉紅色的物質(zhì)，這是未洗滌盡的氫氧化鈉與酚酞產(chǎn)生的物質(zhì)顏色，終將導(dǎo)致鉀含量偏高。因此，洗滌次數(shù)均不應(yīng)低于12次。洗滌次數(shù)少于12次的原始結(jié)果與不少于12次的正確結(jié)果比較見表1。

If the inspector does not wash enough, the pink substance can be clearly seen on the dried crucible. This is the color of the substance produced by the unwashed sodium hydroxide and phenolphthalein, which will eventually lead to a high potassium content. Therefore, the washing times should not be less than 12 times. See Table 1 for the comparison between the original results of less than 12 times of washing and the correct results of no less than 12 times.

總結(jié)一下在氫氧化鉀產(chǎn)品的主含量氧化鉀檢驗(yàn)中，對(duì)幾個(gè)關(guān)鍵環(huán)節(jié)必須給予足夠的重視，對(duì)可能產(chǎn)生誤差的各種因素要加以避免和克服，才能保證檢驗(yàn)結(jié)果的準(zhǔn)確度。

To sum up, in the test of potassium oxide in the main content of potassium hydroxide products, sufficient attention must be paid to several key links, and various factors that may cause errors must be avoided and overcome to ensure the accuracy of the test results.

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