Guidelines for care & Use of Dry Solvent Stills [Example]

Mineral acids (HCl, HNO 3 and H 2 SO 4 ), ammonium hydroxide (NH 4 OH), and Phosphoric Acid
(H3PO4) can legally be disposed of as instructed in Armour, M.A., Hazardous Laboratory Chemicals
Disposal Guide, 2nd edition. Boston: CRC Press, 1996, under the following conditions:
a. The acids must be completely neutralized and this must occur as a definite part of the
experimental procedure, preferably at the end.
b. Dilute with at least 1:10 dilution of acid to H 2 O before neutralizing
c. Contaminants present in the acid must be less than 1% total
(A copy of this book is kept in the stockroom #110.)
Do not dispose of hydrofluoric acid or perchloric acid in this manner. It should be given to the
waste companies, as should spent chromerge (chromic acid/H 2 SO 4 ) cleaning mixtures.
The listed procedures for all four mineral acids are basically as follows:
Wear suitable gloves, such as nitrile rubber gloves (i.e., the blue, green, or yellow gloves located in
the stockroom, room #110), a laboratory coat, and eye protection while slowly diluting the concentrated
acid or further diluting less concentrated acids in a suitable container, such as a large beaker or a lab sink
with a drain plug, or a large standard heavy-duty polyethlene pan.
Add baking soda (sodium bicarbonate), sodium carbonate, calcium carbonate, or soda ash slowly
into the diluted solution until neutralization is complete, i.e., until vapors of CO2 don‟t rise from the
mixture. Pour the resulting solution down the drain with at least 50 times its volume in H20. All of this
should preferably be done in a fume hood.
Reaction equations for Neutralizations of Acids:
2 HCl + Na2CO3 � 2NaCl + CO2 + H2O
2HNO3 + Na2CO3 � 2NaNO3 + H2O + CO2
H2SO4 + Na2CO3 � Na2SO4 + H2O + CO2
Ammonia can similarly be disposed of using dilute hydrochloric acid as the neutralizing agent.
Reaction equations for neutralizations of ammonium hydroxide and phosphoric acid:
NH4OH + HCl � NH2Cl + H2O
2 H3PO4 + 3 Na2CO3 � 2 Na3PO4 + 3 H2O + 3 CO2
43