A second teenager has been arrested by police investigating five linked acid attacks in London.
A 15-year-old was arrested on Friday morning on suspicion of grievous bodily harm and robbery following the "hideous" attacks on Thursday night.
A 16-year-old was already being held on suspicion of the same offences after being identified near the scene of the attacks by CCTV.
Both are being held in custody at a north London police station and Scotland Yard said they are treating the attacks, which took place within 90 minutes, as linked.
All five victims were taken to hospital, with one described as having life-changing injuries.
The assaults involved a pair on a moped attacking other moped riders and allegedly stealing two bikes.
The Metropolitan Police dismissed rumours all the victims were food delivery drivers set up in advance of the attacks.
Those attacked were described as being "from a variety of backgrounds", while officers urged potential witnesses to come forward with information and photos and videos they may have recorded.
Chief Inspector Ben Clark, from Hackney Borough, said: "These are hideous offences and must have been very frightening for all of the victims.
"Of late we have seen more attacks using corrosive substances in London.
"I would urge businesses and parents to challenge those who they think may be trying to obtain or carry these substances as this could help prevent serious offences and life changing injuries being caused."
At the start of the rampage, at 10.25pm, a 32-year-old man was approached as he rode towards the Hackney Road junction with Queensbridge Road.
The two attackers tossed a corrosive substance in his face before one jumped on his moped and rode away.
Police dowsed the victim with large bottles of water, said witness Sarah Cobbold.
The man went to an east London hospital but his injuries are not being treated as life-threatening or life-changing.
Twenty minutes later, at around 10.50pm, a 44-year-old man was sprayed with liquid on the Upper Street junction with Highbury Corner, Islington.
The victim was taken to a hospital in north London, but there is not yet an update on his condition.
At 11.05pm, the two attackers swooped on a third man, a 24-year-old, on Shoreditch High Street, throwing acid in his face but stealing nothing.
His injuries are life-changing, police said.
Within 15 minutes they struck again, throwing the corrosive liquid at a man on Cazenove Road and causing "life-changing" facial injuries.
The final assault was reported at 11.37pm, when a 33-year-old man was confronted as he sat on his moped in traffic on Chatsworth Road.
He was also sprayed in the face, the moped stolen and both attackers fled. The victim made his way home before calling police, after which he was taken to hospital with no update on his condition.
Witness John Moody told Sky News he heard a "really nasty scream" and "banging, shouting and crashing".
"They (police) took the guy's shirt off and started dowsing him in cold water," he said. "As they were doing this more police arrived and also more food delivery moped riders."
A petition to restrict the sale of acid and bring in a licence system currently has more than 360,000 names
The head of London's Metropolitan Police, Cressida Dick, said she is looking at whether a change in the law is needed.
She told LBC Radio: "I don't want people to think this is happening all over London all the time, it is really not, but we are concerned because the numbers appear to be going up.
"We will arrest people, we will enforce the law as we can, and we are working very closely with the Home Office to try to see if there is any changes in the law required."
Labour MP Stephen Timms, who will lead a House of Commons debate on the issue on Monday, has called for tougher sentences and suggested that carrying sulphuric acid without a good reason should be treated as seriously as carrying a knife.
The attacks come days after a man appeared in court charged with throwing acid at a 21-year-old woman and her cousin.
Resham Khan, 21, and Jameel Muhktar, 37, were left with life-changing injuries after the attack in Beckton, east London, on 21 June.
There was another acid attack in east London on Easter Monday, leaving two people at a nightclub partially blinded and others injured.
:: Any witnesses, anyone with information or in possession of footage of these incidents should contact police via 101 or via Twitter @MetCC. To give information anonymously call Crimestoppers on 0800 555 111 or visit crimestoppers-uk.org.