HazMat Tool — substance information

Magnesium silicide

HMT 15 June 2026

UN / ID: UN 2624
Hazard class: 4.3
Packing group: II
ERG guide: ERG 138
Special provisions: SP A19, SP A20, SP IB7, SP IP2, SP IP21, SP T3, SP TP33, SP W31, more…
Source: 49 CFR §172 (15 June 2026)

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Magnesium silicide

Magnesium silicide, Mg2Si, is an inorganic compound of magnesium and silicon. As-grown Mg2Si usually forms black crystals; they are semiconductors with n-type conductivity and have potential applications in thermoelectric generators Wikipedia

Emergency Response Guide No. 138

Hazardous Materials Table

Source: 49 CFR §172 (15 June 2026)

(3) Hazard Class

4.3
Dangerous when wet materials

(4) Identification number

UN 2624

(5) Packing Group

(6) Labels

(7) Special Provisions (§172.102)

×Note:
Special provisions may be very complex. The extracts are taken from 49 CFR §172.102. Please be careful with the information, as necessary, additional conditions may be applied that are not written here. Please check the original source and report bugs.

A19

Combination packagings consisting of outer fiber drums or plywood drums, with inner plastic packagings, are not authorized for transportation by aircraft.

Browse special provision A19

A20

Plastic bags as inner receptacles of combination packagings are not authorized for transportation by aircraft.

Browse special provision A20

IB7

_{Authorized IBCs:} Metal (11A, 11B, 11N, 21A, 21B, 21N, 31A, 31B and 31N); Rigid plastics (11H1, 11H2, 21H1, 21H2, 31H1 and 31H2); Composite (11HZ1, 11HZ2, 21HZ1, 21HZ2 and 31HZ1); Wooden (11C, 11D and 11F).
_{Additional Requirement:} Liners of wooden IBCs must be sift-proof.

Browse special provision IB7

IP2

When IBCs other than metal or rigid plastics IBCs are used, they must be offered for transportation in a closed freight container or a closed transport vehicle.

Browse special provision IP2

IP21

When transported by vessel, flexible, fiberboard or wooden IBCs must be sift-proof and water-resistant or be fitted with a sift-proof and water-resistant liner.
Large outer packagings:
Large outer packagings:
§ 178.275(d)(2)
§ 178.275(d)(3)
§ 178.275(d)(2)
§ 178.275(d)(3)
Prohibited
§ 178.275(d)(2)
§ 178.275(d)(3)
Prohibited
Prohibited for liquids.
Prohibited
§ 178.275(d)(3)
§ 178.275(d)(3)
Prohibited
Prohibited
§ 178.275(d)(3)
§ 178.275(d)(3)
§ 178.275(d)(3)
§ 178.275(d)(3)
Prohibited
Prohibited
Prohibited for liquids. § 178.275(d)(2).

Browse special provision IP21

Minimum test pressure (bar)	2.65
Minimum shell thickness	§ 178.274(d)(2)
Pressure-relief requirements	Normal
Bottom opening requirements	§ 178.275(d)(2)

Browse special provision T3

TP33

The portable tank instruction assigned for this substance applies for granular and powdered solids and for solids which are filled and discharged at temperatures above their melting point which are cooled and transported as a solid mass. Solid substances transported or offered for transport above their melting point are authorized for transportation in portable tanks conforming to the provisions of portable tank instruction T4 for solid substances of packing group III or T7 for solid substances of packing group II, unless a tank with more stringent requirements for minimum shell thickness, maximum allowable working pressure, pressure-relief devices or bottom outlets are assigned in which case the more stringent tank instruction and special provisions shall apply. Filling limits must be in accordance with portable tank special provision TP3. Solids meeting the definition of an elevated temperature material must be transported in accordance with the applicable requirements of this subchapter.

Browse special provision TP33

W31

Non-bulk packagings must be hermetically sealed.

Browse special provision W31

W40

Non-bulk bags are not allowed.

Browse special provision W40

(8) Packing Authorizations (§173.***)

(8A) Exceptions	151	see 49 CFR §173.151
(8B) Non-bulk	212	see 49 CFR §173.212
(8C) Bulk	241	see 49 CFR §173.241

(9) Quantity Limits

(9A) Passenger aircraft/rail	15 kg
(9B) Cargo aircraft only	50 kg

(10) Vessel stowage

(10A) Location

Stowage category “B” means

(i) The material may be stowed “on deck” or “under deck” on a cargo vessel and on a passenger vessel carrying a number of passengers limited to not more than the larger of 25 passengers, or one passenger per each 3 m of overall vessel length; and
(ii) “On deck only” on passenger vessels in which the number of passengers specified in paragraph (k)(2)(i) of this section is exceeded.

Source: 49 CFR §172.101(k)

(10B) Other

13	see 49 CFR §176.84
85	see 49 CFR §176.84
103	see 49 CFR §176.84
148	see 49 CFR §176.84

Source: 49 CFR §176.84

Segregation chart for load, transport, and storage

This chart shows whether loading, transport, or storage with other hazard classes is permitted, prohibited, or restricted. Based on 49 CFR §177.848.

Hazard class	8	7	6.1	5.2	5.1	4.3	4.2	4.1	3	2.3B	2.3A	2.2	2.1	1.6	1.5	1.4	1.3	1.1/1.2
1.1/1.2
1.3
1.4
1.5
1.6
2.1
2.2
2.3A
2.3B
3
4.1
4.2
4.3
5.1
5.2
6.1
7
8

	Must not be loaded, transported, or stored together in the same vehicle or facility.
	May be loaded, transported, or stored together.
	May be loaded, transported, or stored together only with restrictions.

Similar substances

UN / ID	Proper shipping name	Hazard class
UN 1869	Magnesium or Magnesium alloys with more than 50 percent magnesium in pellets, turnings or ribbons	4.1
UN 2950	Magnesium granules, coated, particle size not less than 149 microns	4.3
UN 1459	Chlorate and magnesium chloride mixture solid	5.1
UN 3407	Chlorate and magnesium chloride mixture solution	5.1
UN 1418	Magnesium, powder or Magnesium alloys, powder	4.3
UN 1928	Methyl magnesium bromide, in ethyl ether	4.3
	Magnesium dross, wet or hot	Forbidden
UN 1419	Magnesium aluminum phosphide	4.3
UN 1622	Magnesium arsenate	6.1
UN 1473	Magnesium bromate	5.1
UN 2723	Magnesium chlorate	5.1
UN 2004	Magnesium diamide	4.2
UN 2853	Magnesium fluorosilicate	6.1
UN 2010	Magnesium hydride	4.3
UN 1474	Magnesium nitrate	5.1