Detectives are looking into the attack after a 67-year-old man was injured in Larkhall.
Around 11.25pm on Friday, 11 February, 2022, a man was at home in Machanhill when he opened his door to two men.
The pair then attacked him and threw the substance in his face.
Emergency services attended and the man was taken to University Hospital Wishaw. He remains in hospital in a serious condition.
Police are treating the incident as attempted murder.
The two men ran off in the direction of Field Road and were last seen walking on Hareleeshill Road towards John Street.
The first suspect was wearing a dark coloured medium-length jacket. He wore a hood and had white trainers and a white carrier bag.
The second suspect was dressed all in black, also with his hood up.
At the time of the attack at least one of the suspects is thought to have been wearing a surgical type face mask.
Police have been carrying out door-to-door enquiries and are continuing to review relevant CCTV footage for any additional information on the suspects.
Officers say they are still working to piece together a motive.
Detective Inspector Susie Cairns said: “We are working to establish the full circumstances of this attack and the reason for it. A man has been left seriously injured and it’s imperative we trace the men responsible. I am appealing to anyone who was in the area around the time of the incident to contact us with any information.
“We know the suspects were walking up Hareleeshill Road towards John Street so I would ask any motorists with dash cams who were in those locations to check the footage and pass on any images which could assist our ongoing investigation. All information is vital as we piece together the motive for this attack.”
Police say they will maintain a presence in the area with additional officers on patrol for community reassurance.
Anyone with information is asked to call Police Scotland via 101.