The second arrest was made this morning.
A 15-year-old boy was arrested at an address in Stoke Newington on suspicion of grievous bodily harm and robbery.
A 16-year-old male had been previously arrested on suspicion of the same offences in Kingsbury Road, N1 in the early hours of Friday after he was identified near the scene of the offences by local authority CCTV operators.
Both suspects are in custody at a north London police station.
Chief Inspector Ben Clark, from Hackney Borough, said:
"This is a fast moving investigation and we have made two arrests today. However, I would like to ask the public for their help. Each of these offences took place in busy locations and we know there may be witnesses who have not yet contacted us. If you saw something or managed to film or photograph anything that might help us please get in touch.
"These are hideous offences and must have been very frightening for all of the victims. I'm aware of rumours circulating that the victims were all food delivery riders set up in advance of the attacks. This is not the case. All victims were riding mopeds at the time of the attacks, but were from a variety of backgrounds.
"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."
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