Hello. I work for an institution with a historical collection. One item in our collection, a Hardens blue star hand grenade fire extinguisher has recently cracked and started leaking its contents...which are now creating a white crust all over the exterior of the bottle. I think early variations of these extinguishers typically contained a bicarbonate or salt water solution...and then at some point they switched to carbon tetrachloride. Could leaking carbon tetrachloride cause an efflorescence...such as is visible in the attached image? Or is this white efflorescence a good indication the contents are a less harmful salt water solution? We have no date on the bottle, so I don't know if this is a 19th century or 20th century version.
Nothing to fear, safety-wise! The earliest Hardens "Grenade" fire extinguishers (1880) were called that because they were tossed into a fire, where they broke, releasing the carbon tetrachloride inside. That produced both an immediate local cooling effects as well as oxygen removal (blanketing) to put out a fire. The later versions are an enhancement of the simple portable pressurized water extinguisher by adding the sodium bicarbonate as an additional extinquishing agent.
A leak of any size of a container containing carbon tetrachloride would produce a temporary frost from condensed atmospherice moisture due to the cooling effect of the expanding CCl4. However, ALL of the CCl4 would eventually (quickly) be released, and the frost would disappear on warming.
The residue your picture shows could definitely come from a release of a bicarbonate solution. Any solution left in the cylinder would be water and bicarbonate. Only the amount that the internal pressure of the cylinder and the orientation of the crack would have been released.
Just wanted to add my voice of agreement with Steven. As a former firefighter and chemistry professor, I've seen a few of these things over the years. I'd hope that their collectible value is based on the exterior and not the contents!
As noted in the first reply, carbon tetrachloride would evaporate with no residue. Your grenade contains a salt solution, and the residue on your grenade certainly looks like baking soda. According to the British National Trust, the version sold there in the 19th century contained a water solution of ordinary salt (NaCl) and ammonium chloride (NH4Cl): Fire extinguisher grenade 1145704.6 | National Trust Collections