Minnesota Mining and Manufacturing Co. reported a 27.8 per cent in profits for the third quarter on a 12.2 per cent sales increase, contributing to record third quarter and nine month results.

The diversified manufacturing firm reported net income of $108.8 million (94 cents a share) in the third quarter, compared with $85.2 million (74 cents) in the same 1976 period.

Sales for the quarter totaled $1.032 billion, up from $919.3 million for the third quarter of 1976.

For nine months, net income rose 21.8 per cent on a sales increase of 12.6 per cent. Income was $304 million ($2.63) compared with $249.6 million ($2.17) in the January-September period last year. Sales rose to $2.972 billion from $2.639 billion for the comparative period.

Raymond H. Herzog, board chairman, said 3M's U.S. business continued to do well and foreign operations performed very well considering the weakness of many overseas economies.

"While profit margins are higher this year, there is potential for further improvement, and this is being stressed throughout the organisation," said Herzog.

American Express Co. reported third quarter net income of $76 million ($1.06 a share) compared with $53.4 million (81 cents) a year ago.

Revenue for the travel and financial services company rose to $914.5 million from $768 million.

For the nine months, net income was $103 million ($2.69) compared with $139 million ($1.93) in the previous year. Revenue was $2.52 billion compared with $2.16 billion.

Continental Corp. said its third quarter net income rose to $62 million ($2.31 a share) from $27 million ($1.02) for the same period a year ago.

Continental heads a group of diversified financial companies that includes Continental Insurance, Diners Club and more than 80 other affiliates around the world.

"The improvement in our primary property and casualty results reflects better planning, better management at all levels and a thankful absence of catastrophe storms," said Continental chairman John B. Ricker Jr.

Weyerhaeuser Co., the timber giant, earned 57 cents a share in the third quarter against 61 cents a year ago despite a rise in sales to $900 million from $756 million.

The drop in earnings was caused by an increase in the effective income tax rate, the company said.

For nine months, Weyerhaeuser had an increase in profits to $237 million ($1.80 a share) on sales of $2.4 billion against $220 million ($1.67) a year earlier on sales of $2.1 billion.

The revival of the housing and other construction industries brought the improvement in sales, the company said.

Amax, Inc., a diversified natural resources developer, said its third quarter profits fell to $30 million (78 cents a share) from $37.6 million ($1.08) a year ago.

The Greenwich, Conn., company said the decline was due to lower earnings from its copper operations, increased interest expense and reduced investment tax credits.

Sales totaled $293.5 million compared with $303.7 million a year ago.

Amax said copper operations resulted in a loss due to lower shipments caused by a strike at its Cateret, N.J. refinery and a generally weak market for the metal.

Aluminum Co. of America reported an increase in third quarter profits to $42.6 million ($1.21 a share) from $39.1 million ($1.13) a year ago. Sales and operating revenues totaled $828.3 million compared with $776.8 million a year ago.

Nine months results totaled $150.4 million ($4.31) compared with $104.2 million ($3.01) a year ago, with sales of $2.59 billion compared with $2.18 billion.

R.J. Reynolds Industries reported a gain in the third quarter to $103.5 million in profits ($2.12) against $91.8 million in profits ($2.12) against $91.81 mil-billin compared with $1.5 billion.

Nine month results totaled $291.6 million ($6.01) compared with $263 million ($5.57) on sales of $4.8 billion against $4.2 billion.

Alcan Aluminum Co. said its third quarter profits increased sharplyto $53.6 million ($1.32 a share) compared to $10.4 million (27 cents) a year ago. Sales jumped to $745.5 million from $654 million.

Nine months results were $138.8 million ($3.43) compared with $21 million (57 cents) on sales of $2.28 billion compared with $1.96 billion.

American Brands said its third quarter earnings increased to $39.62 million ($1.47 a share) from $32.51 million ($1.20) a year ago on sales of $1.175 billion against $1.039 billion a year ago.

Its nine months results totaled $122.84 million ($.57) compared with $101.52 million ($3.80) a year ago on sales of $3.376 billion against $3.085 billion.

Inland Steel Co. reported a decline in third quarter profits to $19.7 million (95 cents a share) compared with $22.4 million ($1.08) a year ago. Sales were $680.7 million, up from $615.8 million for the same period last year.