bulk density and tapped density
松密度和紧密度
the bulk density of a solid is often very difficult to measure since the slightest disturbance of the bed may result in a new bulk density. moreover, it is clear that the bulking properties of a powder are dependent on the “history” of the powder (e.g., how it was handled), and that it can be packed to have a range of bulk densities. thus, it is essential in reporting bulk density to specify how the determination was made.
固体的松密度的测量很困难，测量时，轻微的震动就会导致松密度的不同。因此，可以知道粉末的松散性取决于粉末的来历。而且压紧之后，会有一个密度范围。因此，报告松密度时，必须说明结果是如何得到的。
because the interparticulate interactions that influence the bulking properties of a powder are also the interactions that interfere with powder flow, a comparison of the bulk and tapped densities can give a measure of the relative importance of these interactions in a given powder. such a comparison is often used as an index of the ability of the powder to flow. the bulk density often is the bulk density of the powder “as poured” or as passively filled into a measuring vessel. the tapped density is a limiting density attained after “tapping down,” usually in a device that lifts and drops a volumetric measuring cylinder containing the powder a fixed distance.
微粒的相互作用不仅影响粉末的松散性，而且影响粉末的流速。粉末的松密度和紧密度的比较，可以看出微粒的相互作用的相对重要性的量度标准。这样一个比较常被用于粉末流动能力的一个指标。粉末的松密度的测量就是直接将粉末倾入一个量器。紧密度是被叩后的极限密度，通常使用一个设备，将一个装有固定高度粉末的量筒举起，落下。
bulk density
bulk density is determined by measuring the volume of a known mass of powder sample that has been passed through a screen into a graduated cylinder (method i) or through a volume-measuring apparatus into a cup (method ii).
松密度的测量是将已知质量的样品的粉末过筛进入一个量筒（方法ⅰ）或通过一个体积测量器进入一个容器（方法ⅱ）。
method i—measurement in a graduated cylinder
方法ⅰ:用量筒测量
procedure— unless otherwise specified, pass a quantity of material sufficient to complete the test through a 1.00-mm (no. 18) screen to break up agglomerates that may have formed during storage. into a dry 250-ml cylinder introduce, without compacting, approximay 100 g of test sample, m, weighed with 0.1% accuracy. if it is not possible to use 100 g, the amount of the test sample and the volume of the cylinder may be modified and the test conditions specified with the results. select a sample mass having an untapped apparent volume of 150 to 250 ml. a 100-ml cylinder is used for apparent volumes between 50 ml and 100 ml. carefully level the powder without compacting, if necessary, and read the unsettled apparent volume, vo, to the nearest graduated unit. calculate the bulk density, in g per ml1, by the formula:
步骤：除非有特殊说明，先将足够量的样品过筛（1.00-mm 编号18）去除存储时可能形成的大块。称取约100g（至0.1%）的样品置250-ml的量筒，不要压实。如果不可能用100g样品，样品量和量筒大小可以改变。报告结果时说明测试条件。样品的质量的选择为不叩实外观体积为150至250ml.一个100-ml的量筒可用于的外观体积为50ml和100ml之间。小心地夷平样品粉末不要压实，如果需要，读取未处理的外观上的体积，v0至zui接近的刻度。计算松密度，g/ml ,用下列公式：
(m) / (vo).
generally replicate determinations are desirable for the determination of this property.
一般需重复测量。
method ii—measurement in a volumeter
方法ⅱ：用体积计测量
the apparatus
装置如图一：
fig. 1. scott volumeter.
conforming to the dimensions in astm b 329-90 (scott volumeter)2, consists of a top funnel fitted with a 1.00-mm (no. 18) screen or the screen opening specified in the individual monograph. the funnel is mounted over a baffle box containing four glass baffle plates over which the powder slides and bounces as it passes. at the bottom of the baffle box is a funnel that collects the powder and allows it to pour into a cup of specified capacity mounted directly below it. the cup may be cylindrical (25.00 ± 0.05 ml volume with an inside diameter of 30.00 ± 2.00 mm) or a square (16.39 ± 0.05 ml volume with inside dimensions of 25.4 ± 0.076 mm).
符合美国材料实验协会b 329-90的尺寸（斯科特体积计），顶部有一个漏斗，上面放一个合适的1.00mm的筛子（除非有特殊说明，编号18）,漏斗装在一个由4个玻璃挡板组成的导料槽上，粉末顺着玻璃挡板滑行和反跳。在导料槽的底部是一个用来聚拢粉末的漏斗，在漏斗的正下方放置一个容量的样品收集容器。此容器可以是圆柱的（体积25.00±0.05ml，内径30.00±2.00mm）或正方的（体积16.39±0.05ml，内径25.4±0.076mm）.
procedure— allow an excess of powder to flow through the apparatus into the sample receiving cup until it overflows, using a minimum of 25 cm3 of powder with the square cup and 35 cm3 of powder with the cylindrical cup. carefully scrape excess powder from the top of the cup by smoothly moving the edge of the blade of a spatula perpendicular to and in contact with the top surface of the cup, taking care to keep the spatula perpendicular to prevent packing or removal of powder from the cup. remove any material from the sides of the cup, and determine the weight, m, of the powder to the nearest 0.1%. calculate the bulk density, in g per ml, by the formula:
步骤：将样品粉末倒入设备，直至样品收集容器的粉末溢出。用至少25m3的粉末洒在正方形状的样品收集容器上或用至少35m3的粉末洒在圆柱状的样品收集容器上，垂直方向地用一个抹刀在容器的顶部平稳的移动，仔细地刮掉多余的粉末。注意抹刀要在垂直方向运动，防止从容器压紧或切除粉末。移除容器边缘的任何物质，称粉末的质量，m,到0.1%，用下列公式计算粉末的密度，g/ml
(m ) / (vo)
in which vo is the volume, in ml, of the cup. generally replicate determinations are desirable for the determination of this property.
v0 样品收集容器的体积，ml
一般需重复测量。
tapped density
振实密度
tapped density is achieved by mechanically tapping a measuring cylinder containing a powder sample. after observing the initial volume, the cylinder is mechanically tapped, and volume readings are taken until little further volume change is observed. the mechanical tapping is achieved by raising the cylinder and allowing it to drop under its own weight a specified distance by either of two methods as described below. devices that rotate the cylinder during tapping may be preferred to minimize any possible separation of the mass during tapping down.
振实密度是用机械振动装有粉末的量筒。观察量筒的初始的体积之后，用机械轻叩量筒，直到体积不再变化为止，记录体积。用机械轻叩量筒，就是将量筒举起至下述2个方法规定的高度，然后让量筒自由落下。当轻叩时，设备使量筒不停的旋转是的，这样，当量筒自由落下时，可以将任何可能的粉块的分离减到zui少。
method i
方法ⅰ
procedure— unless otherwise specified, pass a quantity of material sufficient to complete the test through a 1.00-mm (no. 18) screen to break up agglomerates that may have formed during storage. into a dry 250-ml glass graduated cylinder (readable to 2 ml) weighing 220 ± 44 g and mounted on a holder weighing 450 ± 10 g introduce, without compacting, approximay 100 g of test sample, m, weighed with 0.1% accuracy. if it is not possible to use 100 g, the amount of the test sample may be reduced and the volume of the cylinder may be modified by using a suitable 100-ml graduated cylinder (readable to 1 ml) weighing 130 ± 16 g and mounted on a holder weighing 240 ± 12 g. the modified test conditions are specified with the results. carefully level the powder without compacting, if necessary, and read the unsettled apparent volume, vo, to the nearest graduated unit.
步骤：除非有特殊说明，先将足够量的样品过筛（1.00-mm 编号18）去除存储时可能形成的大块。称取约100g（至0.1%）的样品置250-ml的已干燥的玻璃量筒（重220±44g,zui小刻度=2ml），安装在一个支持物上（重450±10g），样品不要压实。如果不可能用100g样品，样品量可以减少，可以改用一个合适的100-ml的量筒（重130±16g，zui小刻度=1ml），安装在一个支持物上（重240±12g）。大小可以改变。报告结果时说明测试条件。小心地夷平样品粉末，不要压实，如果需要，读取未处理的外观上的体积，v0，至zui接近的刻度。
mechanically tap the cylinder containing the sample by raising the cylinder and allowing it to drop under its own weight using a suitable mechanical tapped density tester that provides a fixed drop of 14 ± 2 mm at a nominal rate of 300 drops per minute. unless otherwise specified, tap the cylinder 500 times initially and measure the tapped volume, va, to the nearest graduated unit. repeat the tapping an additional 750 times and measure the tapped volume, vb, to the nearest graduated unit. [note—fewer taps may be appropriate, if validated, for some powders.] if the difference between the two volumes is less than 2%, vb is the final tapped volume, vf . repeat in increments of 1250 taps, as needed, until the difference between succeeding measurements is less than 2%. calculate the tapped density, in g per ml, by the formula:
使用合适的振实仪，用机械轻叩装有样品的量筒，将量筒举起14±2mm，然后让量筒自由落下，每分钟落下300次。除非有特殊说明，先轻叩量筒500次，测量振实后的体积，v0，至zui接近的刻度。再轻叩量筒750次，测量振实后的体积，v1，至zui接近的刻度。[注意：对于某些粉末，如果经过了验证，可以适当地减少轻叩的次数]如果2次测量的体积的差异小于2%， v0是初始的体积，v1是zui后的体积。如果需要，再轻叩量筒1250次，直至随后测量的差异小于2%。用下列公式计算振实密度，g/ml.
(m ) / (vf).
generally replicate determinations are desirable for the determination of this property.
一般需重复测量。
method ii
方法ⅱ
proceed as directed under method i except that a suitable mechanical tapped density tester that provides a fixed drop of 3 mm (±10%) at a nominal rate of 250 drops per minute is used.
除将量筒举起3mm，每分钟轻叩250次之外，其余操作与方法ⅰ相同。
measures of powder compressibility
粉末可压缩性测量
the compressibility index and hausner ratio are measures of the propensity of a powder to be compressed. as such, they are measures of the relative importance of interparticulate interactions. in a free-flowing powder, such interactions are generally less significant, and the bulk and tapped densities will be closer in value. for poorer flowing materials, there are frequently greater interparticle interactions, and a greater difference between the bulk and tapped densities will be observed. these differences are reflected in the compressibility index and the hausner ratio.
粉末的可压缩性指标和豪斯纳比率是被压缩后的粉末的倾向的量度标准。同样地，它们是微粒相互作用的相对重要的量度标准。对于易流动的粉末，这样的作用几乎没有意义，松密度和振实密度的值相差不大。对于流动性差的粉末，常常有较大的微粒相互作用，测得的松密度和振实密度的值有较大的差异。这些可由可压缩性指标和豪斯纳比率反映。
compressibility index— calculate by the formula:
可压缩性指标 —可由下面的公式计算
hausner ratio— calculate by the formula:
豪斯纳比率—可由下面的公式计算
备注：
1 the density of solids normally is expressed in g per cm3 and that of liquids is normally expressed in g per ml; however, because powder volumes are measured in cylinders graduated in ml, bulk and tapped densities will be expressed in g per ml. by definition, the ml and the cm3 are equivalent volumes.
固体的堆密度的单位一般用g /cm3，液体的堆密度的单位一般用g / ml，然而，因为粉末的体积是用量筒测量，以毫升表示，松密度和紧密度单位都是g / ml表示。根据定义，ml和cm3相当。
2 apparatus may be purchased from scientific supply companies and is usually described as a “scott, schaeffer and white paint pigment volumeter.”
该设备可从科学供应的公司购买，通常又称为“斯科特，谢弗和白色油漆颜料容积计。
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