Alkaline fluoroborate in fluorophosphate glass free of beryllium

A fluorophosphate glass free of beryllium and having a refractive index n.sub.e between 1.40 and 1.46, an Abbe value v.sub.e between 85 and 94 and a high positive anomalous partial dispersion +.increment.v.sub.e between 19 and 28 produced by a process comprising melting a mixture consisting essentially of the following components:

• (a) methaphosphate(s):
• about 7 to 15% by weight Al(PO.sub.3).sub.3 alone, or
• about 0 to 15% by weight Al(PO.sub.3).sub.3 and 0 to 11% by weight of an alkali metaphosphate, or
• about 0 to 15% by weight (Al(PO.sub.3).sub.3 and about 0 to 5% by weight of at least one alkaline earth methaphosphate, wherein the sum of all metaphosphates is between about 7 and 15% by weight;
• (b) fluorides:
• about 0 to 6% by weight LiF
• about 0 to 12% by weight KHF.sub.2
• about 3 to 12% by weight MgF.sub.2
• about 9 to 28% by weight CaF.sub.2
• about 6 to 16% by weight SrF.sub.2
• about 4 to 13% by weight BaF.sub.2
• about 22 to 31% by weight AlF.sub.3
• wherein the proportion of the alkaline earth fluoride amounts to between about 23 and 52% by weight;
• and
• (c) alkaline fluoborate:
• about 5 to 29% by weight NaBF.sub.4, wherein boron ions are introduced by means of the complex fluoborate to prevent formation of B.sub.2 O.sub.3.