制茶工业在我国历史悠久,随着茶叶生产的不断发展,有关茶尘的职业性危害正在广泛深入地调查研究,而茶尘中游离二氧化硅含量则是作为评价茶尘危害的一项常用指标。以往我们用钼兰比色法进行测定,但由于测定中所使用的镍坩埚不能用洗液清洗,因而每次测定无法求得镍坩埚的本底浓度致测定结果不准。如1983年第四季度,我们在芜湖茶厂生货、熟货车间按工种分别采样21点次,测得游离二氧化硅含量最小值为1.9％,最大值为37.1％,X=9.66％。而同期在同样的工种点上采样,用焦磷酸法测得的结果最小值为1.3％,最大值为13.24％,X=4.76％。而且在粉尘浓度非常低的拣茶 The tea industry has a long history in our country. With the continuous development of tea production, the occupational hazards of tea dust are being investigated extensively and deeply. The content of free silica in tea dust is a commonly used measure to evaluate the harm of tea dust index. In the past, we measured with molybdenum blue colorimetric method. However, since the nickel crucible used in the measurement can not be washed with the washing liquid, the background concentration of the nickel crucible can not be obtained after each measurement. For example, in the fourth quarter of 1983, when we were in the Wuhu tea factory, the cooked workshops were sampled 21 times respectively according to the types of work. The minimum free silica content was 1.9% and the maximum value was 37.1%, X = 9.66%. In the same period, the same sampling point was sampled. The minimum value of pyrophosphate method was 1.3%, the maximum value was 13.24%, X = 4.76%. And in the dust concentration is very low pick tea