What are the grades of chemical reagents? What is the standard of division?

What are the grades of chemical reagents? What is the standard of division? Chemical reagents produced in China are generally divided into four grades according to purity:

1. Excellent purity (GR);

2. Analytical purity (AR);

3. Chemical purity;

4. Experimental reagent (LR).

In addition, there are spectrally pure reagents.

What are the grades of chemical reagents, and what are the criteria for the classification of reagent grades? There are 225 general varieties (class I reagents), which are essential varieties. The second kind of reagents are used in almost all fields, with about 1800 ~ 2000 varieties. There are about 3000 ~ 6000 varieties of the three reagents.

There are 225 kinds of chemical reagents in China. According to the national standards of People's Republic of China (PRC) and the standards issued by the former Ministry of Chemical Industry, they are expressed in three grades: excellent purity, analytical purity and chemical purity. These 225 kinds of chemical reagents, in the form of standards, laid the foundation for the content of chemical reagents in China. The content determination of other chemicals is based on this, and its content is determined by measurement. Therefore, the quality of these chemical reagents is very important. At the same time, these 225 kinds of chemical reagents have become basic varieties because of their wide application. These 225 varieties have been marked in the catalogue of chemical reagents. In addition, there are special reagents, the production volume is very small, almost on demand, and the quantity is generally specified by users.

What are the grades of chemical reagents? According to purity, they are divided into excellent purity, analytical purity and chemical purity.

What are the criteria for dividing inland waterways? According to the international standard GBJ 139-9, the waterway grade is divided into 7 grades.

The lowest order is

The channel scale standard of class seven, that is, 50-ton ships.

Grade 6100t

Five-level 300 tons

Four-stage 500t

Grade III1000t

Secondary education 2000 tons

First-class 5000 tons

American waterway classification index

The channel scale of the United States takes the channel depth as the grading index, combined with the selected tonnage and ship type. For example, the water depth of the Mississippi River waterway in the United States is divided into five grades, namely 1.83m, 2.74m, 3.66m, 4.26m, 12.20. The tonnage of the corresponding typical segmented barge and self-propelled barge is less than 760 tons and 960 tons respectively.

What is the division standard of 88 constellations? 1922 The General Assembly of the International Astronomical Union sorted out the constellations and their names used in history, scientifically re-divided them according to the right ascension circle and the right declination circle on the celestial sphere, and determined them as 88 constellations commonly used in the modern world. For example, the south vestibule (also known as the vestibule of heaven) was cancelled because of its large scope, and it was divided into four seats: bottom, stern, compass and sail. 1928 The International Astronomical Union officially announced 88 constellations commonly used in the world. At the same time, it is based on the vernal equinox and equator of 1875. According to the different positions of the 88 constellations on the celestial sphere and the appearance of the stars, they are divided into five regions, namely, the Northern Celestial Constellation (5), the Polaris Constellation (40 ~ 90, 19), the Twelve Constellations (12 constellation near the ecliptic on the celestial sphere) and the Zodiac Constellation (19). The 88 constellations in the whole day are: North Sky Constellation (5 constellations): Ursa minor (closest to the north celestial pole), Ursa major, Cassiopeia, Draco and Cepheus.

Polaris constellation (19): Scorpio, Andromeda, Lupo, Auriga, Canis major, Foxes, Cygnus minor, Perseus, Shepherd, Pentecost, Backrow, Corona Nordica, Tmall, Lyra, Dolphin, Pegasus, Triangle.

Zodiac (12): Cancer, Aries, Gemini, Aquarius, Virgo, Leo, Taurus, Pisces, Capricorn, Scorpio, Libra and Sagittarius.

Twelve constellations (10): Sagittarius, Canine, Eagle, Ophiuchus, Ophiuchus, Sextant, Ophiuchus, Unicorn, Orion and Whale.

Southern Constellation (***42): Temple of Heaven, Picture Frame, Fly, Mountain Case, India, Tian Yan, Flying Fish, Long Ruler, Swordfish, Clock, Rhododendron, Southern Triangle, Compass, Dragonfly, Telescope, Hydra and Southern Cross (1999).

* * * What is the standard of division! From the concept of "* * *" in Buddhist scriptures, that is, the concept of "virginity", it is not authentic "* * *" if it is leaked. But in the modern sense, it must be combined with a different * * * (not a simple encounter, but * * *) to lose qualification. Must be with a different * * * (not a simple encounter, it is going to happen * * *) to lose the qualification of * * *.

What is the classification standard for heavy vehicles? Heavy vehicles: refer to M-class and N-class vehicles with a maximum gross mass greater than 3500Kg. A car train consisting of a heavy tractor and a heavy trailer. It is used to carry large goods whose size and weight exceed the limits stipulated by highway traffic regulations.

A single flat trailer can be assembled vertically and horizontally, forming a variety of variants to adapt to the shipment of large goods with different weights and sizes. There are usually three variants:

① Combined flat trailer. It is formed by splicing one or several single flat trailers according to the required length.

② Long-distance trailer. According to the requirements of the supporting position of long goods, the two flat trailers are separated by a proper distance, and each trailer is equipped with a rotatable bearing frame, so that the supporting positions at both ends of the long goods are fixedly installed on the bearing frames of the two flat trailers, so that the goods and the vehicles form a whole.

③ Bridge trailer. The two flat trailers are separated by a certain distance, each with a hydraulic lifting platform, and a bearing bridge is installed between the two lifting platforms, so that the front and rear trailers, the lifting platform and the bearing bridge are connected into a whole. The load-bearing bridge is the load-bearing part. Bridge trailer is used to transport large goods with a large proportion. In addition, on the basis of single flat trailer, other variants can be formed, such as clamp trailer, concave low flat trailer, gooseneck semi-trailer and so on, to meet different use requirements.

What are the criteria for distinguishing living things from nonliving things? What are the criteria for distinguishing living things from nonliving things?

What are the criteria for distinguishing living things from nonliving things?

As an organism, it should have the following basic characteristics: 1. Metabolism II. Growth, development and reproduction. Inheritance, variation and evolution. Sensibility and movement. Stability of internal environment Strictly speaking, there is nothing between living things and non-living things.

What is the time division standard of constellations? twelve astrological signs

Aries constellation

3.2 1-4.20

Taurus constellation

4.2 1-5.2 1

Gemini

5.22-6.2 1

Cancer constellation

6.22-7.22

Le Signe du Lion

7.23-8.23

virgo

8.24-9.23

libra

9.24- 10.23

Scorpius

10.24- 1 1.22

Sagittarius

1 1.23- 12.2 1

Capricorn palace. Compare CAPRICORNUS

12.22- 1.20

Aquarius constellation

1.2 1-2. 19

fishes

2.20-3.20