Vigorously exothermic compounds in contact with water

1.

The violent exothermic compounds in contact with water generally include concentrated sulfuric acid, chlorosulfonic acid, acid halide, sulfuryl halide, acid anhydride , thionyl chloride , phosphorus trihalide, phosphorus oxyhalide, phosphorus pentahalide, phosphorus pentoxide , aluminum trihalide , Boron trihalide, etc.

AlCl ₃ and BBr _{3 will} decompose violently when they meet with water, so they must be slowly added to the water under constant stirring

BBr3 is a formidable, white-smoke, highly corrosive liquid, which is toxic and sensitizing to the human body.

2.

1.

Mercury vapor is highly toxic.

2.

For waste liquids such as mercury oxide, organic mercury, mercury salt, etc.

It is also possible to add sodium sulfide and alum (potassium aluminum sulfate dihydrate) to the waste liquid to promote the precipitation of mercury ions in the form of HgS.

For organic mercury waste liquid containing alkyl mercury, it must be decomposed and converted into inorganic mercury before being processed

The toxicity of mercury is that whether it exists as a simple substance or a compound, it may pollute the air and eventually pollute rivers, lakes, seas and soil

3.

PCC, pyridinium dichromate (PDC) and Jones reagent are the restrictive oxidants of hexavalent chromium, including other hexavalent chromium reagents.

Quenching method: Add excess isopropanol until the color of the system changes from orange or red to green (the characteristic color of trivalent chromium).

It is best to use sodium bisulfite reduction method, the reaction formula is

4H ₂ CrO ₄ +6NaHSO ₃ +3H ₂ SO ₄ =2Cr ₂ (SO ₄ ) ₃ +3Na ₂ SO ₄ +10H ₂ O

It is safe to change the solution from orange-red or orange-yellow to green

Cr ₂ (SO ₄ ) ₃ +6NaOH=2Cr(OH) ₃ ↓+3Na ₂ SO ₄

4.
Cadmium waste liquid

Use slaked lime [Ca(OH) ₂ ] to convert cadmium ions into hardly water-soluble Cd(OH) ₂ precipitation
.
That is, add slaked lime to the cadmium waste liquid, adjust the pH to 10.
6~11.
2, stir well and place to separate the precipitate.
When the filtrate is detected to be free of cadmium ions, it can be neutralized
.

5.
Lead waste liquid

Use slaked lime to convert the divalent lead into insoluble lead hydroxide , and then use the aluminum salt delead method for treatment
.
That is, add slaked lime to the waste liquid, adjust the pH to 11, so that the lead in the waste liquid is precipitated by lead hydroxide, and then add aluminum sulfate to reduce the pH to 7-8, that is , the co-precipitation of aluminum hydroxide and lead hydroxide is generated After placing it to make it fully clarified, the filtrate is detected to be free of lead, the waste liquid is discharged, and the precipitate is separated
.

6.
Other metal reagents

Some metal mixtures or coordination metal reagents such as sodium amalgam, zinc powder, zinc amalgam, zinc-copper coupling agent have important practical value in organic synthesis, but they must not be thrown into the trash can casually, otherwise under aerobic conditions Combustion may occur in contact with organic compounds, which requires attention
.

Waste metal reagents and metal reagents processed after the reaction (including filtered diatomaceous earth filter residue, etc.
) need to be quenched, and generally can be quenched by acidification
.

There are five treatment methods for Zinc Qiqi in the laboratory.
The better methods are concentrated sulfuric acid method and sodium hydroxide method
.
Concentrated sulfuric acid method: heating the waste zinc amalgam with concentrated sulfuric acid to obtain non-hazardous mercury sulfate and zinc sulfate
.
Sodium hydroxide method: The waste zinc amalgam is reacted with sodium hydroxide to obtain sodium zincate, which is separated from mercury
.
The reaction rate of this method is slower than that of the sulfuric acid method
.

The collected heavy metals mercury, cadmium, chromium, lead, tin or heavy metal salt precipitation must all be handed over to a qualified disposal unit for harmless disposal
.