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 BULK DENSITY AND TAPPED DENSITY

                        松密度和緊密度

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.

固體的松密度的測(cè)量很困難,，測(cè)量時(shí)，輕微的震動(dòng)就會(huì)導(dǎo)致松密度的不同,。因此,，可以知道粉末的松散性取決于粉末的來(lái)歷,。而且壓緊之后，會(huì)有一個(gè)密度范圍,。因此,，報(bào)告松密度時(shí)，必須說(shuō)明結(jié)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.

微粒的相互作用不僅影響粉末的松散性,，而且影響粉末的流速。粉末的松密度和緊密度的比較,，可以看出微粒的相互作用的相對(duì)重要性的量度標(biāo)準(zhǔn),。這樣一個(gè)比較常被用于粉末流動(dòng)能力的一個(gè)指標(biāo),。粉末的松密度的測(cè)量就是直接將粉末傾入一個(gè)量器。緊密度是被叩后的極限密度,，通常使用一個(gè)設(shè)備,，將一個(gè)裝有固定高度粉末的量筒舉起，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).

松密度的測(cè)量是將已知質(zhì)量的樣品的粉末過(guò)篩進(jìn)入一個(gè)量筒（方法Ⅰ）或通過(guò)一個(gè)體積測(cè)量器進(jìn)入一個(gè)容器（方法Ⅱ）,。

Method I—Measurement in a Graduated Cylinder

方法Ⅰ:用量筒測(cè)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, V_o, to the nearest graduated unit. Calculate the bulk density, in g per mL¹, by the formula:

步驟：除非有特殊說(shuō)明，先將足夠量的樣品過(guò)篩（1.00-mm 編號(hào)18）去除存儲(chǔ)時(shí)可能形成的大塊,。稱取約100g（至0.1%）的樣品置250-mL的量筒,，不要壓實(shí)。如果不可能用100g樣品,，樣品量和量筒大小可以改變,。報(bào)告結(jié)果時(shí)說(shuō)明測(cè)試條件。樣品的質(zhì)量的選擇為不叩實(shí)外觀體積為150至250mL.一個(gè)100-mL的量筒可用于的外觀體積為50mL和100mL之間,。小心地夷平樣品粉末不要壓實(shí),，如果需要，讀取未處理的外觀上的體積,，V0至zui接近的刻度,。計(jì)算松密度，g/mL ,用下列公式：

(M) / (V_o).

Generally replicate determinations are desirable for the determination of this property.

一般需重復(fù)測(cè)量,。

Method II—Measurement in a Volumeter

方法Ⅱ：用體積計(jì)測(cè)量

The apparatus 

裝置如圖一：

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).

符合美國(guó)材料實(shí)驗(yàn)協(xié)會(huì)B 329-90的尺寸（斯科特體積計(jì)）,，頂部有一個(gè)漏斗，上面放一個(gè)合適的1.00mm的篩子（除非有特殊說(shuō)明,，編號(hào)18）,漏斗裝在一個(gè)由4個(gè)玻璃擋板組成的導(dǎo)料槽上,，粉末順著玻璃擋板滑行和反跳。在導(dǎo)料槽的底部是一個(gè)用來(lái)聚攏粉末的漏斗,，在漏斗的正下方放置一個(gè)容量的樣品收集容器,。此容器可以是圓柱的（體積25.00±0.05mL，內(nèi)徑30.00±2.00mm）或正方的（體積16.39±0.05mL,，內(nèi)徑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:

步驟：將樣品粉末倒入設(shè)備,，直至樣品收集容器的粉末溢出。用至少25m3的粉末灑在正方形狀的樣品收集容器上或用至少35m3的粉末灑在圓柱狀的樣品收集容器上,，垂直方向地用一個(gè)抹刀在容器的頂部平穩(wěn)的移動(dòng),，仔細(xì)地刮掉多余的粉末。注意抹刀要在垂直方向運(yùn)動(dòng),，防止從容器壓緊或切除粉末。移除容器邊緣的任何物質(zhì),，稱粉末的質(zhì)量,，M,到0.1%,，用下列公式計(jì)算粉末的密度，g/mL

(M ) / (V_o)

in which V_o is the volume, in mL, of the cup. Generally replicate determinations are desirable for the determination of this property.

V0 樣品收集容器的體積,，mL
一般需重復(fù)測(cè)量,。

TAPPED DENSITY

振實(shí)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.

振實(shí)密度是用機(jī)械振動(dòng)裝有粉末的量筒。觀察量筒的初始的體積之后,，用機(jī)械輕叩量筒,，直到體積不再變化為止，記錄體積,。用機(jī)械輕叩量筒,，就是將量筒舉起至下述2個(gè)方法規(guī)定的高度，然后讓量筒自由落下,。當(dāng)輕叩時(shí),，設(shè)備使量筒不停的旋轉(zhuǎn)是的，這樣,，當(dāng)量筒自由落下時(shí),，可以將任何可能的粉塊的分離減到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, V_o, to the nearest graduated unit.

步驟：除非有特殊說(shuō)明,，先將足夠量的樣品過(guò)篩（1.00-mm 編號(hào)18）去除存儲(chǔ)時(shí)可能形成的大塊,。稱取約100g（至0.1%）的樣品置250-mL的已干燥的玻璃量筒（重220±44g,zui小刻度=2mL），安裝在一個(gè)支持物上（重450±10g）,，樣品不要壓實(shí),。如果不可能用100g樣品，樣品量可以減少,，可以改用一個(gè)合適的100-mL的量筒（重130±16g,，zui小刻度=1mL），安裝在一個(gè)支持物上（重240±12g）,。大小可以改變,。報(bào)告結(jié)果時(shí)說(shuō)明測(cè)試條件。小心地夷平樣品粉末,，不要壓實(shí),，如果需要，讀取未處理的外觀上的體積,，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, V_a, to the nearest graduated unit. Repeat the tapping an additional 750 times and measure the tapped volume, V_b, 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%, V_b is the final tapped volume, V_f . 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:

使用合適的振實(shí)儀,，用機(jī)械輕叩裝有樣品的量筒,，將量筒舉起14±2mm，然后讓量筒自由落下，每分鐘落下300次,。除非有特殊說(shuō)明,，先輕叩量筒500次，測(cè)量振實(shí)后的體積,，V0,，至zui接近的刻度。再輕叩量筒750次,，測(cè)量振實(shí)后的體積,，V1，至zui接近的刻度,。[注意：對(duì)于某些粉末,，如果經(jīng)過(guò)了驗(yàn)證，可以適當(dāng)?shù)販p少輕叩的次數(shù)]如果2次測(cè)量的體積的差異小于2%,， V0是初始的體積,，V1是zui后的體積。如果需要,，再輕叩量筒1250次,，直至隨后測(cè)量的差異小于2%。用下列公式計(jì)算振實(shí)密度,，g/mL.

(M ) / (V_f).

Generally replicate determinations are desirable for the determination of this property.

一般需重復(fù)測(cè)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.

除將量筒舉起3mm，每分鐘輕叩250次之外,，其余操作與方法Ⅰ相同,。

MEASURES OF POWDER COMPRESSIBILITY

粉末可壓縮性測(cè)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.

粉末的可壓縮性指標(biāo)和豪斯納比率是被壓縮后的粉末的傾向的量度標(biāo)準(zhǔn)。同樣地,，它們是微粒相互作用的相對(duì)重要的量度標(biāo)準(zhǔn),。對(duì)于易流動(dòng)的粉末，這樣的作用幾乎沒(méi)有意義,，松密度和振實(shí)密度的值相差不大,。對(duì)于流動(dòng)性差的粉末，常常有較大的微粒相互作用,，測(cè)得的松密度和振實(shí)密度的值有較大的差異,。這些可由可壓縮性指標(biāo)和豪斯納比率反映。

Compressibility Index— Calculate by the formula:

 可壓縮性指標(biāo) —可由下面的公式計(jì)算

Hausner Ratio— Calculate by the formula:

豪斯納比率—可由下面的公式計(jì)算

備注：

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.

固體的堆密度的單位一般用g /cm³,，液體的堆密度的單位一般用g / mL,，然而，因?yàn)榉勰┑捏w積是用量筒測(cè)量,，以毫升表示,，松密度和緊密度單位都是g / mL表示,。根據(jù)定義，mL和cm³相當(dāng),。

²  Apparatus may be purchased from scientific supply companies and is usually described as a “Scott, Schaeffer and White Paint Pigment Volumeter.”

該設(shè)備可從科學(xué)供應(yīng)的公司購(gòu)買,，通常又稱為“斯科特,，謝弗和白色油漆顏料容積計(jì),。

Auxiliary Information— Please check for your question in the FAQs before contacting USP.

USP32–NF27 Page 226

Pharmacopeial Forum: Volume No. 31(3) Page 909